Search Engine Optimization divided it to two types,On page and off page optimization.Off site SEO contains backlinks and social signals.To increase your ranking in  SERP's you need to have quality of backlinks from other authority sites.As i before said backlinks importance.Here iam giving you some ways to build quality of backlinks to your site,Lets check.....

1. Submit Guest Post to Others Blog
2. Comment on others blog and be sure that blog is related to you or not,if not ignore that site.
3. Start relevent threads in forum and link back it to your blog.
4. Link to Your Blog in Forum Signature (Only high quqlity forums)
5. Do regularly  use Discussion Boards by linking to your blog in threads like Quora is a high quality discussion board.
6. Ask questions related to your blog content in Yahho Answers.And link to your blog in  your question.
7. Use Blogging  Communities by submitting blog posts to them.
8. Write a Answers in Yahoo answers and use source as your site address.
9. Exchange links related to Your niche,Be sure it should be naturally.
10. Submit your Blog to top Blogging Directories
11. Submit your Blog to Top Social Networking Sites.
12. Use press Releases
13. Submit Your rss feed to rss directories
14. Convert your Blog Posts to PDF Formatt and submit it to Top document sharing sites.
15. Do interview with Top Bloggers and share it in social media,their fans will be link back you.
16. Make use of Web 2.0 sites to promote your Blog.
17. Write High Quality of Content ,It will Automatically Brings You Lot of Quality of Backlinks.
18. Submit Your Blog to Dmoz.Another Directeries use this directory.
19. Do use Google Groups And Yahoo Groups.
20. Create a Wikipedia page  For Your Self and include your link in resource section.
21. Donate to charity sites and They will link back you.
22. Submit Your Images to Image directories.
23. Join in Blogging Contests.
24. Submit Your Blog to Local directories.
25. Write on About.com and link to your blog in it.
26. Create a Youtube Videos about your Blog Post.
27. Get listed in paid Directories like Yahoo Directory.
28. Start Your Affiliate Programme.