If you have a good established website you can buy software like SEO Elite or IBP to find other web masters with relevant website to trade links with, it's a very powerful way to increase your rankings, if you find good authority websites to trade links with you could see results within a week.
However webmasters won't talk to you if you have a lame website, so unless your website is well established with good pr I would suggest writing articles. Back in the day you could write a single article and submit it to hundreds of article directories but now all the search engines are clamping down on article spamming.
However you could still go and submit new articles to different directories which allow backlinks with anchor text, It's going to take time but at the end of the day you get backlinks from relevant articles on websites with high page rank.
If you don't mind writing articles you should at least write a new article each day based on the specific keyword your trying to rank for and remember to include the keyword in your anchor text and submit it to the following directories:
PR 6 Directories
And these directories are seen as authorities on the search engines, you will always come across articles from the sites mentioned above. So take advantage and write articles to get yourself good powerful backlinks.
I won't advise you to comment on blogs because you won't be guaranteed the backlink, sometimes the webmaster may delete your comment and you lose a valuable backlink so this method can be unreliable. However with articles you will get permanent one way high pr backlinks for free with no hassle, except writing the articles of course.
So to sum up your question, the quickest way is to already have an established website so you can easily trade backlinks with other webmasters, however if you can't go with that option there are article directories which will take a whole lot longer but it will still deliver good results in time.
I would suggest writing more unique content but content will benefit you more towards traffic than backlinks, to focus on your main goal you need backlinks from other websites which have high page rank.
Because if you think about it backlinks is like a vote and with you creating content on your website would be just like creating duplicate votes, which won't be as valuable as having someone esle vote for you.
So it's not a bad thing but you will see better faster results by getting backlinks from other sites.