Forum Posting
Blog Commenting and Posting
Classified Posting
Business Listing

These all are good for getting back links.

If, you want to create back links then these activity is good like

Forum Posting
Blog Commenting and Posting
Business Listing
Classified
Directory Submission

Try to find a dofollo forum where you can add friends. Then you add friends with huge number of posts.
Post->Friends profile>Your profile-> your site.
This links are so powerfull.

Classified, Directory submission,forum post, social bookmarking, forum post,blog, articles submission, press release, SMO etc...

technique use to make the backlinks:
blog posting
blog commenting
Directory submission
forum posting
yahoo answer

First think comment only on those blog that is related to your niche, when you read your niche blog then you are easily unable to give your view on that.

forum posting
directory submission
social bookmarking

To create backlinks one has to adopt the different SEO methods, these methods are very useful as SEO point of view, the methods we use here are social bookmarking, forum posting, blog commenting, image backlinks, press release etc.

1. Article submission
2. Blog submission
3. Press release
4. Forum posting

1. Directory submission
2. Posting at High PR forum with your signature
3. Link Exchange
4. Blog Commenting
5. Also try buying some backlinks from freelancers on sites like SEOclerks.

Link building is the technique, used to build the back links to your site. The techniques are
Directory submission
Social bookmarking submission
Forum posting
Posting classifieds sites
Yahoo answers

You can get Backlink from many source such as
forum posting
blog commenting
article posting
directory submission
classified submission
ping
document sharing
video sharing
image sharing

Post your information in High Page rank of Directory Submission, Social Bookmarking, Blog Posting, Article Submission . Also need to work in SMO.