WOW there are so many tried and true ways, below are just a few
1. Good SEO practices, having your keywords placed and ready is key
2. Forum marketing at targeted forums based on your niche. If you answer questions properly you can become a valid professional in your niche
3. Blog commenting, not as good as forum but a nice way to drive targeted traffic.
4. Provide a Ebook or something branded with a link back to your site and allow giveaway right, let it go viral.
5. Yahoo Answers, again become the expert.
6. Someone above said this already, but Social media is HUGE.
Good Luck