There are all sorts of complicated theories and concepts out there about how to get your stuff listed high up in the search engines. I'm sure some have merit to them, but I've found that with SEO, much like everything in life, simplicity and the fundamentals are key. For example, with keyword research, find phrases which have low supply and high demand. I know it sounds ridiculously simple, but I can't tell you how many times I've seen this fundamental concept ignored and people complain about their stuff not getting high up in the search engines. Any other common sense to add here?