If you're just starting you're at a disadvantage - most schemes won't accept you until you have a certain number of visitors, reasonable PR and Alexa ranking. AdSense would be my number 1 recommendation too, but most people find they can earn more doing sponsored posts to begin with. You might like to try: Blogsvertise Blogitive ReviewMe SponsoredReviews Like I said - some of these might not accept you at first.
Blog about what you like and worry about making money later. You can make money blogging about anything. The key is creating a site full of interesting content first. Start with content, then worry about making money. If you're in it just to make money, you're going to find yourself having somewhat of a tough time. There are already millions of people trying to blog about making money in order to make money, and most are miserable failures.
You shouldn't start trying to monetize your site until you get a decent amount of daily traffic, or you will just drive people away. A good rule of thumb is to have 200+ unique visitors and 500+ page views a day before you start to monetize