It depends on the nature of the business for some businesses it works and for some business it doesn't so depending upon different aspects it can be tested.
On page techniques are those techniques which are done on website pages like writing great titles, use of header tags, alt tags, great user experience, loading time, quality content etc.
Alt tag is the alternate tag which is used when image is not displayed the alt tag is displayed and search engine reads the alt tag so it is a good factor to use keyword as the alt tag
Keywords density is the number of occurrences of keyword within a content but it as long as you are writing in a natural way it is not that much important.
Meta keywords are not important as Google won't give any credit for meta keywords. In the past they were considered very important but nowadays they are not necessary.
In short do-follow links pass link juice and no-follow links don't pass link juice so if you don't want to pass page rank then mark the link as no-follow.