What you need to focus on are ‘long tail keywords’, these are the easiest to rank for not only as a newbie in affiliate marketing, but as an internet marketeer in general.
So what are long tail keywords? These are phrases containing at least 3 words that are typed in the search engines (Google for example) for people to find information on.

For example if you’re looking to promote a product on dating, you could write down things like ‘getting my ex back’, ‘how to get my ex back’, ‘ways to get my ex back’. There are lots of people who are searching for ways to win back their ex-es and thankfully Clickbank has enough products that you can promote for years.
Or if you’re looking at the diet niche, long tail keywords might be ‘the green tea diet’, ‘ways to lose weight fast’, ‘get rid of fat’, etc. Diet, fasting, fat and dating are NOT long tail keywords. These are whole markets and you’d really need gloves of iron to even try competing with these general terms.

One of the best sources of finding great long tail keywords is Micro Niche Finder. I can’t recommend this product enough, it’s really a superb piece of craftsmanship. With this software you can make your whole market research and much more. You can buy it directly here from the author.