A Web spider is a program which is used by search engine to find what is new on Internet(website). This process is called Crawling. Web Crawler makes a begining by crawling the pages of websites. Then it indexed the words and contents found on that website. 

But remember..
Low quality content
Pussy content
irrelevant content
advertise, advertise, and only advertising
This kind of content is harmful for your business. So be careful while you write your content. 

A 301, or permanently moved, is a redirect that alerts the crawlers that your content has moved permanently (that is, it's not coming back).

A 302, or "Found"/temporarily moved, is a redirect that alerts the crawlers that your content has moved temporarily (that is, it may come back later, like when you have it back in stock).

When it comes to SEO, a 301 passes the link information and updates the information in the search engine index so that the index will have the new address.  If you're moving a whole site over to a new domain (or whatever), then you should use this. You're still going to have a bit of time where things are kind of haywire in the index while Google (or whoever) reindexes everything, but it's better than you dropping out entirely.

A 302, well, it's not really a thing for SEO.  Sure, you can use it, but the crawlers will occasionally come back to check on things, because it's not permanent.  Whatever links, etc. you have coming to this page will continue to be all about this page and not the new page.  Again, this is for temporary stuff, which can happen, but usually not in the name of SEO.

Good luck.

Search engine crawlers does not crawl the No-Follow links they only crawl Do-Follow links.

It is good if you post links on dofolow websites. 

It's depends on the situation or else both having their own importance.

Suppose you want to block indexing of only one page in Search Engine, than in this case robots meta tag will be a good option instead of robots.txt. Because if you are blocking a single page by using robots.txt then there is some chances to appear that URL in SERP, For Example check below FB page that is blocked by using robots.txt and its still appearing in SERP.
Suppose you want to block indexing of directory or folder then in this case robots.txt is best option. Because if we are planning to use robots tag then we have to add robots tag on all page and its time consuming process.

Crawling Budget:
One thing to notice is that the Google will still crawl the complete page even though we block any pages by using robots meta tag. But its vice-versa in case of robots.txt. So if you want to save Search Engine Crawl budget then robots.txt is good.

A sitemap is a structured list of all of the pages within a particular website. Sitemap can also be a structured list of images, videos. Two kinds of sitemaps are predominantly used on the websites; XML & HTML. The XML sitemap is used to let search engines know what information to index for search engine results. An HTML sitemap provides your list to users who are visiting your website - it helps them find the information that they are seeking. 

Accelerated Mobile Pages (AMP) are all the craze now! Search for any trending topics in Google, you can find the news carousel marked with little grey lightening ⚡ symbol. ⚡ - Symbol for Accelerated Mobile Pages - the name simply says it all.

Ignoring mobile search traffic is no longer an option. Mobile online presence has now become a necessity as the mobile traffic keeps increasing year-after-year. AMP is a Google-backed project that aims at speedy delivery of mobile content using stripped down code called as AMP HTML.
Static webpages not influenced by user actions/behaviour can be built using AMP. These pages load much faster than normal HTML, with 15-85 percent speed improvement and Google pre-render support.

Google Trends is a public web facility of Google Inc., based on Google Search, that shows how often a particular search-term is entered relative to the total search-volume across various regions of the world, and in various languages. ... On September 27, 2012, Google merged Google Insights for Search into Google Trends. source : wikipedia

Yes Google Plus is one of my favorite Social Networking Site. and Facebook too

Knol has been discontinued as of May 1, 2012 

Best service of google are google search engine, gmail, google AdSese 

Google Panda is a change to Google's search results ranking algorithm that was first released in February 2011. The change aimed to lower the rank of "low-quality sites" or "thin sites", and return higher-quality sites near the top of the search results.
Soon after the Panda rollout, many websites, including Google's webmaster forum, became filled with complaints of scrapers/copyright infringers getting better rankings than sites with original content. At one point, Google publicly asked for data points to help detect scrapers better. Google's Panda has received several updates since the original rollout in February 2011, and the effect went global in April 2011. To help affected publishers, Google provided an advisory on its blog thus giving some direction for self-evaluation of a website's quality. Google has provided a list of 23 bullet points on its blog answering the question of "What counts as a high-quality site?" that is supposed to help webmasters "step into Google's mindset".

Google citation is a description for this result is not available because of this site's robots.txt

Social media optimization (SMO) is the use of a number of social media outlets and communities to generate publicity to increase the awareness of a product, service brand or event. Types of social media involved include RSS feeds, social news and bookmarking sites, as well as social networking sites, such as Twitter, and video sharing websites and blogging sites.
Search engine marketing (SEM) is a form of Internet marketing that involves the promotion of websites by increasing their visibility in search engine results pages (SERPs) primarily through paid advertising.[1] SEM may incorporate search engine optimization (SEO), which adjusts or rewrites website content and site architecture to achieve a higher ranking in search engine results pages to enhance pay per click (PPC) listings.

Keyword stemming is a useful tool for web pages and search engine optimization. The process of keyword stemming involves taking a basic but popular keyword pertaining to a particular website and adding a prefix, suffix, or pluralization to make the keyword into a new word. 

Type of PPC
Search advertising
We've all seen PPC search adverts, although you may not know that's what they were. The most common type of search ad can be spotted on Google, although Bing has their own too. If you Google something, you will notice them at the top and bottom of the organic results. By entering the auction to have your business's ad show here, you can advertise exactly where people are searching for your products or services.
Social advertising
If connecting with customers socially is your preferred way of marketing your goods, social PPC might be for you. You can place your ad in your target demographics' newsfeed, or in their social hangouts. You don't even need a large social media presence to have ads running within social media, you simply need an account!
Remarketing
Ever been on a website and then seen their advert pop up somewhere else? You've been remarketed to. This is a really effective method of PPC and targets people that have already shown a genuine interest in your company. Seeing your advert again may just be enough to convince them to convert on your website.

Link blending is the process of building links to your site as well as other authoritative sites. Let's say, for example, you have a website that sells bicycles online, and you convinced one of your female friends, Michelle, who runs a mom blog, to write a blog post about your bicycle site.

The meta description is a ~160 character snippet, a tag in HTML, that summarizes a page's content. Search engines show the meta description in search results mostly when the searched for phrase is contained in the description. Optimizing the meta description is a very important aspect of on-page SEO.

1.Open your site at sites.google.com. 
2.Click Settings > Manage Site. 
3.Click General > Delete this site. A confirmation box will appear. 
4.To confirm that you want to delete the site, click Delete. 

Blog marketing is any process that publicises or advertises a website, business, brand or service via the medium of blogs. This includes, but is not limited to marketing via ads placed on blogs, recommendations and reviews by the blogger, promotion via entries on third party blogs and cross-syndication of information across multiple blogs. 

Email marketing is directly sending a commercial message, typically to a group of people, using email. In its broadest sense, every email sent to a potential or current customer could be considered email marketing. It usually involves using email to send ads, request business, or solicit sales or donations, and is meant to build loyalty, trust, or brand awareness. Email marketing can be done to either sold lists or a current customer database. Broadly, the term is usually used to refer to sending email messages with the purpose of enhancing the relationship of a merchant with its current or previous customers, to encourage customer loyalty and repeat business, acquiring new customers or convincing current customers to purchase something immediately, and adding advertisements to email messages sent by other companies to their customers. 

I recommended AHREF 

If you want to build backlinks to your website, you have to do it with caution and knowledge. You should monitor each backlink you create or earn and verify if it carries any SEO value. Always avoid getting backlinks from pages where you don't have any control.

Step 1: Use a Keyword Research Tool to Find Niche Keywords
Step 2: Refine Your Niche Keyword List
Step 3: Determine How Competitive Your Niche Keyword Phrases Are 

-Title tag – You need a relevant title, not just "Home
Page" Use it for 5 key words. 
-Headings – The search engines view < h> tags as
being terms of emphasis – they give weight to the words within
them. Put key terms in them.
-Bold – Of lesser importance than < h> tags. the
< b> tags still emphasize terms of importance.
-Alt text – Use descriptive short sentences in your alt
tags. If it's a picture of a rose, and you're a florist try "Red
Rose – Available at 'name' Flower Shop" 
-Keyword metatags
– Some engines use them directly, some check them as part of a
validation process – "do they match the content" If they don't
then is this a spam site? 

Yahoo was founded by Jerry Yang and David Filo in January 1994 and was incorporated on March 2, 1995. Yahoo was one of the pioneers of the early internet era in the 1990s. Marissa Mayer, a former Google executive, serves as CEO and President of the company. It is globally known for its Web portal, search engine Yahoo! 

Advertise
This one is so obvious, we're going to look at it first. Paid search, social media advertising and display advertising are all excellent ways of attracting visitors, building your brand and getting your site in front of people. Adjust your paid strategies to suit your goals – do you just want more traffic, or are you looking to increase conversions, too? Each paid channel has its pros and cons, so think carefully about your objectives before you reach for your credit card.
Get Social
It's not enough to produce great content and hope that people find it – you have to be proactive. One of the best ways to increase traffic to your website is to use social media channels to promote your content. Twitter is ideal for short, snappy (and tempting) links, whereas Google+ promotion can help your site show up in personalized search results and seems especially effective in B2B niches. If you're a B2C product company, you might find great traction with image-heavy social sites like Pinterest and Instagram.
Pay Attention to On-Page SEO
Think SEO is dead? Think again. Optimizing your content for search engines is still a valuable and worthwhile practice. Are you making the most of image alt text? Are you creating internal links to new content? What about meta descriptions? Optimizing for on-page SEO doesn't have to take ages, and it could help boost your organic traffic. 

Digital marketing is an umbrella term for the marketing of products or services using digital technologies, mainly on the Internet, but also including mobile phones, display advertising, and any other digital medium.