I've only recently begun affiliate marketing, but am starting to see some results. It's just a middle of the night, when I find the time kind of thing.
But, I was recently on a list building webinar training and one of the guys was a top 100 ClickBank affiliate. So we're talking 6 figure income (he showed us live on the webinar logging into his backend of ClickBank).
This was his method and I agree with it. You write a quick report and give it away for free, but they have to opt-in to your list to get it. Then you immediately try and sell an inexpensive item (less than $10). Then a few days later you promote a higher end offer. Just contact often and be consistent. If you want to email them everyday you can, just start off that way. You don't want to start sending an email a day to a list that hardly heard from you once a month before.
When picking products I like to look for the high-end product first. If it's a subscription based product, all the better. Then based on what that niche is I look for a complementary item in the same niche for under $10 if possible. Now that I have my affiliate products chosen I can write a quick report based on some general information on that niche.
Quick tip for report: If you chose affiliate products that offer free articles and content for affiliate to use, do it. You can easily take an article, or two or three, and combine them into a report. Format it in Microsoft Word and you have a report on topic.