My site is actually useful and has much better information than the sites that are outranking me. My site is informational and I'm not trying to sell anything (but I do make some money off some affiliate links and Adsense) -- I'm not a thin affiliate or anything like that.
I haven't done any real link building and I don't want to do anything remotely fishy. I get about 48k uniques/120k page views a month.
But I need to do something because I'm afraid of being muscled out by the big boys. Any advice?