• Sites where users go and expect to buy something while they are there. E-commerce sites fit the bill here...
• Sites where users go to find specific information on something that they want to buy now. Music and video review sites, vacation information sites, resume building sites, etc. You don't have to actually be selling these types of things; your site can just be a mecca for information pertaining to these things. Then, when the visitor comes to read your content, they are more likely to click on your ads.
• Sites where people who have disposable income and a credit card like to visit. This includes sites with money management, investing and lifestyle content.
• Sites that draw a large amount of new users every day. Free coupon sites and "How to" sites are good examples.
• Sites where people go who expect to read ads. Classified ads and shopping comparison sites fit into this category.

2. Make sure that your visitors don't feel that you just want to grab their money

Give them plenty of relevant and well-written content. If writing isn't your best skill then hire someone to do it for you. Good content brings steady traffic and steady traffic pays the bills.

3. Play by the rules

Google has some very specific Terms of Service https://www.google.com/adsense/policies for participating in their AdSense program. Learn those rules and follow them so you don't lose all of your investment by getting shut out.

4. Use the tools that Google gives you

Google gives you tools for determining the best keywords for your site, measuring ad performance, and setting up different ad "channels" for fine-tuning ad results. These guys and girls are the 800 lb. Gorillas in the Pay-Per-Click market. They didn't build these tools just to keep their programmers busy. Take advantage of their knowledge for they are very big and you are not!

5. Tweak, fine-tune and then tweak again

You should never be happy with your AdSense performance. If it's good, then you need to make it great. If it's great then you need to make it amazing. If it's amazing then you need to take it to the UPS club. The UPS club? Google sends all checks over $10,000 per month to the webmaster via UPS overnight delivery. Now there's a club that I wouldn't mind belonging to.

6. Get more traffic

No matter how much traffic you have, you need more. More eyeballs translate to more clicks. Even if you're only pulling a 2% click-through. That's a lot of clicks when you have thousands of visitors each day.

7. Experiment with new keywords

New keywords can bring new ads and new eyeballs along with it. Set up some new pages on your site and experiment with different content. Once you get something that's working then refer back to Tip # 5.

You can see results in near real time when you use Google's AdWords. Don't be afraid to be different. If something that everyone else is doing doesn't work for you, then invent something that does work and get it on your site.