Which are the most effective link building techniques?

Social Bookmarking
Guest Posting
Internal Links
Web 2.o
Image sharing

@ Kavi_3, can you suggest me top social bookmarking sites which is actually driving traffic to website?

Find blogs and forums related to the content of your site.
Publish articles.
Try to use publications in RCC news feeds.
Answer the questions.
Start your blog.
Add your site to the directories.
Refer not only to your home page.
Leave a guest message

you can also do documnet sharing if you have worth content and also share your content to tier 1 sites

guest posting
profile listing
bussiness listing
image sharing
social media
pdf submission

You need to be where your audience are. If you are building crappy and spammy links it won't help with your SEO.

You need to think of marketing as promoting rather than building spamy links that won't get you anywhere.