first find out who your traffic should be and then find out where there are a large number of them: social media blogs forums classified ads video sites other peoples websites once you know where they are then you need to know how to get them to your site sometimes all it takes is to write posts or comments and for others you will have to do some advertising.
I would say that social media will be the most effective way to get traffic. Depending on your services of course. If you want to buy traffic, do it through Hourlies, it's the most reliable way, but know that you might not be able to have the results you wish to have unless you try hard enough. Then you should try classifieds, directory and article submissions and ofcourse valuable and intresting blog commenting and forums.
I suggest you to promote your website on top SM sites like facebook, linkedin, twitter etc. Definitely you get targeted traffic.
i think from article submission in different directories like ezine, squidoo ect. And also from video submission.
Classified ads, Online giveways, Article Submissions, List Swaps, Help out a reporter, Facebook, deffo YouTube
Google Adwords, Social Media and even Facebook Ads Email Marketing, Directories, Youtube, Purchase Ads Place
Forums like this one are excellent. I love the Big G for finding little niche forums. I have also used yahoo Answers (although that is more difficult these days).
As a traffic supplier i can say that there is no 1 sure way of increasing organic traffic over night to your site. It takes a combination of different elements to eventually have a steady stream of organic traffic to your site. We constantly have to deal have poorly constructed websites or landing pages and then have the owners complain that they have no sales. CONTENT IS KING beyond anything, you have to be offering something that people want and in a tasteful presentation. Its like going into a rundown store expecting to sell high priced items, it just wont happen. Social connections are so important these days they are a must have, non negotiable! If your thinking what my traffic is good for, well it compliments your seo on your site as it will improve rankings faster and will help bring in organic traffic. I'm always open for discussion on it so pm me with any questions, In the mean time take the advice given by others in this thread and your rankings will slowly increase. There is no magic bullet for rankings no matter what anyone tells you.
Content is king...and so is sharing it Article syndication is a great tool to use. Video is another good one as well. If you are going to make a video be creative, original and valuable to visitors.