I've been dabbling online for a couple of years (just recently decided to get serious with new site). PPC didn't perform well for me, but I had decent luck with forum posts and article marketing.
I think a lot of it depends on the product and one's target market. A less tech-savvy market might not respond to Twitter; but if technology is your product, it's a perfect way to prospect. Figure out how your prospects spend their time online, then meet them there.
