what are main points to fallow in link building to avoid penalty?

Keyword diversity
Backlink diversity

What else?

Is there any specific type of links that need to be avoided?

 

Anchor diversity is the most important.

 

Anchor diversity, very low percentage of exact or partial match keyword links and no links created by any software/tool.

 

don't create any link building too fastly, if you do so then its will be way of penalty

 

Thanks for answers. Should i avoid buying links from private/public blog networks as there is risk of them being caught and sites linking out get penalized?

 

Anchor diversity
Platform diversity
Relevancy
Backlink strenght

 

There are a lot of things to consider based on your link building, but it all comes down to two things:
1. Try to make things look as natural as possible (where you get links from, diversity in anchors, relevancy - as others have stated)
2. Accept the fact that at one point or another you will get hit - just the way it is