Submit your site to frivolous directories: There are good directories as well as bad directories. Actually one of the very best directories is the DMOZ Directory. Because Google uses this directory, listing your company in it is certainly one of the best things you can do as far as link building SEO is concerned. The Yahoo Directory and Best of the Web Directory is also a couple of other highly authoritative directories. On the bad side, there are literally 100s of insignificant directories that typically charge around $10 and $20 a submission. They have virtually no traffic as well as no authority and wouldn't even be worth the effort if they charged just $1 per submission.

Posting on forums:

Similar to directory submissions there are good posts as well as bad posts. Posting on forum threads that are not related to your site or are severely outdated is considered spam. In addition posting the same question to 30 different forums is also considered spam, particularly if you are a new member, particularly if you do it all on the same day. Creating a profile on a forum that you never intend to be a part of just to get a link to your site is also one more form of forum spam.

Commenting on blogs:

Legitimate comments, good. Comments are not actually comments but just your keywords, bad. It is especially trying to say nothing of value about the post, but simply add a comment directing people to your site for further information.

Poor link exchanges:

Link exchanges or else reciprocal linking contributes very little to your link equity. If 2 sites are legally related and linking to each other is mutually beneficial, then by all means exchange links. But, for purposes of link building SEO, link exchanges contribute only small value.

Link farms:

This is one of the oldest as well as worst ways of obtaining links. Link farms are just websites created for the purpose of linking as one with all the other sites in the group. Search engines are capable to identify the attributes that link farms use and can filter them from their search results. They may even pull the whole domain from their index, and panelize the entire participating sites.