The only thing I know to do is make sure each page discusses one topic. That helps with contextual ads. Keep in mind, though, that the ads you see are not necessarily the ones your visitors are seeing. If they are seeing interest based ads, then making your pages optimal for contextual ads can only help so much.
What ember said. But ultimately you're probably going to end up with more interest based ads than contextual, just because that's the way it works now. What worked for me was figuring out my audiences, and then trying to attract more people in that particular audience.
1. Block as many non related categories as AdSense permits 2. Block sensitive categories that don't pertain to your content/audience 3. Block domains/Advertiser URLs that don't fit with your content 4. I would also try running text ads only 5. Make sure there are no ads BEFORE content on each page