Here's the BIG secret with respect to SEO...........THERE IS NO BIG SECRET and anyone who tells you there is is a liar. If you employ a 'trick' to get to the top of Google your stay there will be short lived. If you spend hours or days or weeks securing links from poor websites they will have almost no positive impact on your site.
To understand why linking plays an important part in the ever changing Google algorithms you need to understand the origins of Google itself. The Google boys were PhD students, they are/were academics. Academia thrives on peer reviewed papers. These are researched tomes that stand up by covering all their assertions with citations to other research sources. If a paper references another paper the paper being referenced is further validated and so it goes on. In an academic paper you can't for example state that doing X will have result Y unless you say something like doing X will have result Y as proven in 'Why doing X causes Y: Smith, J & Bloggs, F 1997'. Cut the Google boys in half and this philosophy is printed through their core.
As an aside Sir Tim Berners Lee created the web to allow research to be cross referenced in this way using hyper linking.
So, linking is important because it reinforces what you are saying by referencing things that back it up. Creating links just for the sake of it is not going to have such a huge impact - possibly any!
So this takes us to the question of how to secure links. Well that's easy - or rather it isn't - because it boils down to content. Content was, is and always will be king. Create a website - with a fantastic or rubbish design - put dodgy content in it and it will NEVER achieve a solid and LASTING Google ranking. It might rank for a while until the algorithm changes again then it will fall off the face or webland.
On the other hand if you concentrate on creating a killer site with best of breed content then you will build a site that lasts, ranks and works for you.
If you've got money to spend, spend it on creating killer content, you'd be amazed at how the quality links will start coming in if your website has something to say.
So often people put 100% effort into a websites look and feel and 0% effort into the content then expect a page 1 Google position. If you have a site trying to sell stuff and you can't create great content that quality sites would want to link to stick to PPC, that's what PPC is for.
Google is passionate about delivering the BEST results to its users, it's what it lives for. If your site is rubbish Google will eventually wise up to this and your business may loose it's position overnight, trust me on this, there are many well documented case studies to back this up.