what is the most efficient form of linkbuilding?

I've read plenty about on and off-site SEO and understand how and why it works. My problem is that I've got a long list of ways in which links can be built but I'm confused by how to monitor the effectiveness of what I'm doing.

Do you work to a fairly specific strategy for every site you promote or do you create a completely bespoke marketing plan for each project?

My linkbuilding tends to rely heavily on Ezine Articles, Squidoo and more recently guest posting, blog commenting and even just placing my link in a non-niche forum signature has worked quite well.

I know loads of ways to build links but its mostly article marketing which takes ages and I've never really been happy with the traffic results - perhaps poor keyword choice or optimisation?

Basically, I know what to do but not how to do it properly, efficiently and effectively so as to maximise my return-on-effort.

How do I do it properly?