Google AdSense Tips

1.Don't put ads on empty pages.
When I reworked my site, I built a skeleton set of pages that had no content, just titles and some meta tags. I displayed ads on those pages, however. Although all you see are public service ads at first, the very act of displaying ads on a page causes the AdSense web crawler to quickly fetch that page for analysis. A page with good content will thus begin showing relevant paying ads fairly quickly.
If you don't have any content, then, Google will have to guess as what your page is about. It may guess wrong, and so the ads that it displays may not be relevant. You'll have to wait until Google re-crawls the site for the ads to correct themselves. Here is what Google had to say when I asked them about how often the AdSense crawler updates a site:
Thank you for taking the time to update your site. New ads will start appearing on your site the next time our crawler re-indexes your site. Unfortunately at this time, we are unable to control how often our crawlers index the content on your site.
Crawling is done automatically by our bots. When new pages are added to your website or introduced to the AdSense program, our crawlers will usually get to them within 30 minutes. If you make changes to a page, however, it may take up to 2 or 3 weeks before the changes are reflected in our index. Until we are able to crawl your web pages, you may notice public service ads, for which you will not receive any earnings.

2: Don't be afraid to ask questions
If you're wondering about something, don't be afraid to ask Google. So far, they've always responded to my questions within a working day. There are two email addresses to use, depending on the type of question:
Please feel free to email us at adsense-tech@google.com if you have additional technical questions or concerns. For general program or account questions, please email adsense-support@google.com.
Their responses are always very polite, and they appreciate getting problem reports and suggestions.

3: Avoid non-English characters on English pages
This one is a bug, to be honest. My surname is French, and I prefer to write it out correctly with the accent grave on the first "e". Every page on my site would then include at least two accented letters, because my name shows up twice in the footer. On some pages my name shows up two or three more times.
Normally, this wouldn't be an issue. But on some pages the presence of the accented characters is enough to cause AdSense to display non-relevant ads in French. This happens whether the browser indicates a preference for French or not. When I reported this to Google, this is the answer they gave me:
Hello Eric,
Thank you for bringing this issue to our attention.
We are currently working as quickly as we can to address this problem. As soon as we have more information for you, we will email you again.
We appreciate your patience.
Sincerely,
The Google Team
Until this is resolved, I've decided to strip out all accents except on the pages that are actually in French.