Paid traffic works extremely well (some schemes are a waste of money, though).
Start with Google Adwords. Google has the largest volume of user searches, so you'll get the largest exposure.
Google Adwords posts your ad in the search results for your chosen key phrases. The folks who run this website optimized our website for organic rankings (free rankings) but advised us to run a PPC campaign alongside, because that gives you another spot in the search engines. We get 20% more click-throughs when we run a PPC campaign alongside our organic listings.
PPC advertising is especially important if your website doesn't perform well in the search engines. PPC works really well and we highly recommend it.