Google’s penguin was introduced in 2012 and put a high emphasis on the quality of backlinks, reducing spam for links and keywords. Things which should be avoided are those blackhat SEO techniques such as:
- buying backlinks
- exchanging links
- building up unnatual links
- guest posts on unrelated blogs
- keyword stuffing
- over-optimisation of keyword anchor text
If you are a company who was hit by the penguin update, it is important that you focus on getting rid of spammy or low quality backlinks (this can be done manually or using the Google disavow tool). You should try earning high quality backlinks through generating good content which is worthy of sharing. Try to place your keywords naturally, and read through any text you are writing which has links involved, as it is important that it reads as you would expect in English grammar without too many repetitions of keywords.