You can make really good money from a blog, believe me, what you need to do is to allow guest posting on your blog.

You can not only allow guest posting but also start writing for other blogs.

Read out some tips are given in this link....
http://www.problogger.net/archives/2005/12/06/how-bloggers-make-money-from-blogs/
Thnx...

But blog should have some reputation then anyone will write guest post.

good to know that.

I think affiliate marketing is the good way for making money online

    If you have a more specific niche, you might consider soliciting local businesses to advertise on your blog. Generally, this method is utilized by more seasoned bloggers because local businesses are more interested in spending money on more established online publications. By keeping your content fresh and relevant, you can create a sizeable portfolio that will eventually convince businesses to advertise on your blog.

But blog should have some reputation then anyone will write guest post.