If you want to participate with an affiliate programs and want to build a niche website for selling the products, there are some tips before you join the affiliate program, build an optimized website and start selling the products.

1. Do a research about keywords that you gonna use with Keywords Tracker. Find a perfect keywords that people usually use to get to your website. For example: if you type "Insurance", you'll see that "Auto Insurance" is the most used keywords. So now you just find an affiliate program about auto insurance.

2. Start with choosing a domain name containing the keyword if you can. For example: autoinsurance.com or auto-insurance.com (this one is not going to be easy task :()

3. Write an original article about the products that you want to sell. Make sure it also contain the keywords, so you can compete with your competitor for the higher search result.

4. If you have enough money, try to promote you site with PPC (pay per click) program like Adword. This can boost your site visitors and increase your sales. Ofcourse there's a risk of click fraud.

5. Get more backlink to increase your site rank. The higher the rank, the more you'll get to the top of search engine result. You can do this by exchanging link with other site owner. But asking them to exchange link with you are really time consuming. Beside exchanging link, you can get a lot of backlink by submitting your articles to free article directories. These articles will be published by the webmasters on their sites.