Be Clear on Tactics and Strategies: You don't want to cannibalize your affiliate program with your own marketing tactics. Keep in mind that affiliates drive a lot of their business through search marketing. If you are both competing on the same keywords, this can often cause issues. For example, if you don't want them to bid on your brand terms be upfront about this at the very beginning of the program.
Amazon’s affiliate program is the most popular of them all. I don’t participate myself (yet) but the majority of affiliate marketers I know use Amazon because… it’s Amazon. You can review products you have used or write tutorials (eg. how to connect computer to TV) and drop an affiliate link to an HDMI cable… just a couple examples. You may want to build relationships with the manufacturers so you can get products before they’re released – giving you time to create a review before the product is launched and capture sales during peak buying times.