If I could chose the I'd chose the whole world loving my blog and linking back to it naturally. Since that's probably not going to happen my second option would be to go out an find people who would be interested in my blog's content and telling them why my site would be of interest to their visitors. Those are the links that give the greatest benefit...even though they're more work.
if i have need to chouse only one method for blog then sure i will go for blog commenting on related niche dofollow blogs. its free and useful, and we can make as many as we want by posting just 2-3 line content related comment. but i m always use other method too for blog to make quality one way free links. ~blog commenting ~directory submission ~social bookmarking ~forum posting. till now i use only this method and all is working fine for me.
Uploading videos to youtube and others via tubemogul, with your link in the description or subject field.
Uploading videos was never the best thing to do for me. Strange that it is the most important for you...
during this competitive time, no single method of link building will do you much good, not if you are in a competitive niche. you need to launch a diversified link building campaign to make your backlinks look natural in the eyes of search engines and also to outsmart the competition. what your competitors are doing, you need to do all of those and then some.
Sultan- I think you said it all. I agree! No one knows Googles' algorithms but them. Putting your "eggs" or links in one basket is risky, very risky. Don't do it! After a long time on this forum and others and looking at my competitors back links till I am google eyes I have not come to any conclusions but this I do believe. Getting back links from a variety of sources does look the most natural, it keeps you abreast of all aspects of backlinking, and it keeps you from going bonkers from just doing one method of backlinking. Is there a best way - don't know. I change my opinion on that on a daily, if not weekly basis.
You probably can achieve a decent ranking on less compeptive terms just using free methods such as blog commenting, directories, social bookmarking, forum signatures and other free methods.
This is of course thruth, noone should rely only on one method. However question is question and it starts "If you could choose only one.... Theoreticly speaking