It is ok if you only have one blog that can help you generate more income..But the more the merrier..Hehe..This are some of the method that can help you make money by blogging :

1. Join as a Publisher to publish ads from any program.

2. Join Pay Per Post or Pay Per Review program etc.

3. Join to become an affiliates of any program and publish it on your blog.

4. Sell merchandise on your blog.

5. Sell links from your blog.

6. Allow people to advertise on your blog with charges.

7. Make a page or post that includes your services.Any services would do..Hehe..

P/S: Do a lot of research!!