Simple. Read some older threads from this AdSense forum for ideas.
[webmasterworld.com...]

This has been discussed more times than I can count.

Here we go again.

Maybe this will help you:
[webmasterworld.com...]

OMG! They're popping out of the woodwork now.

Absolutely read as many threads here as you can digest in one sitting. Take a break. Repeat over and over again until there are no more threads to read. That will get you prepared to ask questions here - that is IF you still have questions after digesting all of what you've read.

earnings = visits * pages per visit * ad impressions per page * percentage of impressions clicked * price per click

All you have to do is increase one of more of those values, without reducing any of the other values. What could be easier?

Read, then read, read again and then do some reading.

Perhaps my answer sounds a bit annoying.
But what I mean is that your question is so general, it gives me the idea you should first study a bit so that you can ask a more specific question.

[edited by: BrandNewDay at 11:59 pm (utc) on May 10, 2008]

Perhaps a counter question then:
Could you please name one of the topics of your sites?

Here ya' go:
[webmasterworld.com...]

The AdSense library is arguably the best place on the web to learn how to make the most of the AdSense program.

Good luck.
;)