1. Write high quality content on your website, and optimize your content. Find low competition keywords and also try to target some long-tail keywords.
2. Make sure your website is search-engine friendly. Try getting seo audit for your site - you can get this for free on a lot of websites. Fix all the problem areas of your website by analyzing the SEO audit.
3. Write a high quality press release, and submit it to different press release platforms. Make sure you keyword-optimize your press release, and make it news-worthy.
4. Add share buttons on your website's pages. This will help you drive extra traffic to your website.
5. Use Reddit. Reddit has a LOT of traffic potential, but you have to do it the right way. Find some subreddits related to your niche, and start contributing valuable content to these subreddits. You should aim to get your posts upvoted. Once you start to get more "established" in subreddits, you can start sharing links to your website here. If you can get a good amount of upvotes on your links, then you will get TONS of FREE traffic.
6. Write high quality, unique and keyword-optimized articles. Submit them to article directories - I personally like eZineArticles best.
7. Write a short ebook on a topics related to your niche. Include a link to your website on the first few pages, then publish the ebook on Amazon Kindle. Once published, use their promotion tools to set a "free" promotion for your ebook. This means that everyone who downloads your ebook for free, will see the link back to your site. Adding the link in the first few pages will also get you additional free traffic when someone previews your ebook before buying.
8. Build high quality backlinks to your website. Use different types of backlinks - Web2.0, Social Bookmarks, Forum links, Blog comments, etc.
9. Find blogs related to your niche and add a comment with a link to your site on posts. Be sure NOT TO SPAM - provide a meaningful input on the subject.
10. Answer questions related to your niche on different Q/A sites likes Yahoo Answers and Quora. Add a link to your site WITHOUT sounding like you are promoting your site.
11. Offer a free gift to your visitors, and lock the gift with a "pay by tweet" / "pay by like" script. This means your visitors will have to share your website on their social media accounts in order to download the gift - a great way to increase your social presence.
12. Create some PDF documents on different topics in your niche and submit them to document sharing sites. Be sure to include a link back to your website inside the document, as well as in the description of your PDF documents.