All the things are Important in Search engine Optimization.I will suggest u Blog commenting,forum posting and link exchange.
It depends on your website's age and the niche. I wouldn't recommend to do many backlinks in the first two months. Build up your links slowly and constantly and don't forget to look at your competitors. If they are quite young, but have many backlinks and good positions in Google - follow their strategy. I do 25 to 30 backlink everyday.