You should ensure your pages have enough keywords and phrases for what you are trying to target, as the name suggests, Adsense senses what your page is about and shows ads accordingly, hence you need to make sure your page has enough of the keywords you are trying to target.
Sure, it is the same technique as for SEO: Use the proper keyword(s). The super secret secret is: Think about the topic of the page in question (AdSense works largely pagewise). Every page on your site should cover one topic and only one topic. Ask yourself which products your page might serve as a teaser for, then look for suppliers of that product. For example: If you wrote a cellphone review, you'd be interested in ads from hardwarestores. Once you have found suppliers, ask yourself what keywords they would target. If clueless, use Googles own keyword tool to inspect their pages. Pick the keywords you like. Try to rephrase your page's text in a way to include the keywords you found. Note that Google is especially fond of the page title, the URL, the meta description tag and the first paragraph, as those four locations are what get's shown on SERP. (just a small excempt from this article: http://www.onyxbits.de/node/57 )
I would say don't do anything unusual. Just add content and google ads will find their way to your niche.
thanks guys. This site seems to have ads that are spot on: http://www.thisblogwillpaymymortgage.com/ But my art one has all sorts of odd ads: http://sellmoreartonline.com/