If you're planning to make some petty cash with your blog (you can't make money with a Posterous blog right now, at least not through google adsense), I'll list out the path I took to do that.

Before I list out some useless points about blogging I want you to know that the problem with new bloggers like you is you expect too much too soon without working on your blog. When you learn that a blogger is making more money than his/her day job, you are quick to jump into starting your own blog without knowing the fact that the blogger has put in a lot of sweat to earn that kind of income.

Plainly put, I would summarize blogging like this :
 
1. Set up a blog

2. Work on creating content, loads of content (I wrote like 600 posts in the last 11 months on Twi5)

3. Continue creating content until you see some traffic (may be 100 or 200 visitors per day) coming your way through search engines (yeah 'search engines' and not twitter, facebook etc. which cannot really help you gain significant traffic unless you are a john Chow or Guy Kawasaki)

4. Start finding ways to convert your blog traffic to email and feed subscribers. Put up big links asking readers to sign up for your feed. It helps a lot

5. Once you have a good number of feed subscribers (at least a 100+), you can start with tiny little unobtrusive google adsense ads

6. Go with the little tiny ads for a few months, earnings would be meagre but would help you get a start

7. Now, after all this if your traffic has reached aroud 1000+ visitors everyday, start putting those big adsense ads right below the title of your blog posts

8. Adsense earnings would be like $1-$2 for every 1000 visitors to your site

9. Write a 'Make Money Blogging' post :)

P.S. In the midst of all these, never deviate from creating new posts on your blog on a daily basis!

Do you have anything to add to this? May be it would make me earn some more cash through blogging too.