I just found this video from the Creators of SeNuke X and i find it really interesting and worth to watch it.
How to Make Good Links & Find and Delete Bad Links


Also here is their previous video where they talked about penguin update, and how to avoid i.
Or if you were penalized to get out of it.

I tried it on one of my friends website and he got back 90% of traffic before penalization, i guess this is a pretty good result after traffic dropped...