The true correlation between societal signs and search positions is a much argued over topic, but here is a fantastic summary of the topic.
There are lots of ‘black hat’ techniques which may bring the complete weight of a Google penalty back on your website, so it is ideal to refrain from performing the next, even though it resembles a fantastic easy win in the moment.
Overusing keywords in your pages, particularly when they clearly influence the readability of your website.