- Soical Networking - Directories - PPC (pay per click) - Blogs - Audio Ads - Video Ads - Newspaper ads - Banners, signs etc. - Others Lot of us will use multiples from this list, but there are preferences of one over others. Which one is your best choice.
I voted for SEO, as in my opinion it's the best marketing way. However, it really isn't easy to make your site SEO-friendly and get indexed well. Another good marketing option is your DP signature.
In terms of traffic there's nothing that beats a site ranking highly in search engines. Best thing is that it's free, and can be achieved with lots of work and effort when building quality sites.