Many people have different methods. One of my preferred is finding a high PR site, for starting blogs I would aim to PR4-PR6, If you own such a site, a lot better because you own the back links
Having said that, deliver good quality content to the site you are targeting for the backlink, it can be in the form a blog comment, guest post, article or whatever the site may be willing to use.
Just deliver something of value, otherwise your content would be qualified as spammy and you will remain in square 1.
Do this over and over again, be consistent, if your site is new, getting 50 or 100 of these backlinks at the same time would be spammy in the eyes of Google and your site may get penalized, even worse if you dont do it again. but if you get 2 or 3 a week, increasing that number of links from time to time it is ok
Just remember.. Focus in high PR sites, ad deliver great content in a timely basis.
The point with the PR is critical. it is better to have 1 PR4 backlink, rather that 5 PR3.. Hopefully the idea is clear.