none.
onsite:
what you need to do is to smartly stuff kws with proper onpage and structure site with silosing. probably dont repeat one kw more than once or twice. (stuffing kws is dead but if these are different kws then its not dead, its alive and verywell)
+ create good content to increase ux signals and hope they will stay on page, add to favorite and link to it.
offsite:
here all the tricks like emailing, commenting, making friends with bloggers... and all the other bs that marketers recommend, wont help you. what you need is to regularly and intensively create related links either manually or automatically or perhaps both using any means possible. what you need to do is to transfer as much related link juice as possible but heres the trick, majority of links we can create manually like webs 20, forums and profiles are weak as hell and provide little to no push
so in the end, being a good seo and ranking a site means writing good content + mastering onpage, which there are lot of tutorials for + mastering creating backlinks, and this is the hardest, because no one will tell you how to create powerful links, not only everyone is struggling, but also its very valuable info so they cant share