First, I only promote things I believe in (of course). I only use them when I feel they add value to topic and are relevant. And you have to have a disclaimer, to keep it legal (even though it seems like more hassle than it's worth, IMO.)

Amazon is a great affiliate partner because they have so many products (just about everything). That makes it easy because you can sign into one place and link to several different products in a post. Less passwords to keep up with too. The downside is the commission rates are lower than most other affiilates, especially in the beginning because you progressively make more (%wise) the more you sell. Another downside is there are some scam companies that portay themselves as reputable brands on Amazon, and sell knock-off products. So that worries me about Amazon. Therefore, when possible I try to link to the actually company's product. But I do order a lot off Amazon and the products seem to be legit.

I think it makes more sense to put affiliate links in free products, such as blog posts, than in paid products.

Most affiliates have html codes that you put into your posts and either create text links or banners. Some have ways to make them URL links. It depends on the program.

Some of them have 2 tier systems where you can invite others to join the affiliate program and then make money from their sales too. For example, if you sign up here, you can become an affiliate of Body Ecology products and I would make a small commission from your sales too.

All of this is at no extra cost to the buyer, which is nice. I plan on teaching internet marketing in the future so I'll give more pointers when the time comes. But let me know if there's any way I can help in the meantime.