Web 2.0 Sites
The use of web 2.0 sites is very similar to article submissions really. Using hosted web 2.0 platforms such as WordPress.com and Blogger blogs you have the ability to control the page content and engineer backlinks to your website as you wish.
These are typically good second tier link targets (will mention later in the plan of action section).
As well as hosted blogs, these should ideally include a number of different media/page types where you can control the content and leave links such as the following:
– Wiki sites
– PDF/document hosting sites
It’s not really possible to automate these types of links (other than using spun content) so these should be used for second tier sites (more about that later).

Social Indicators
Social indicators is something that I’ve still not had a whole lot of experience with but as time goes on, it will start becoming much more of an important factor especially with Google +1.
The way that rankings used to work in the past was more open to abuse as the only way that Google could determine the quality of a website was through the virtual votes cast in favour of that website by means of other domains linking to it.
Now with Facebook, Twitter and other social networking websites, Google can more easily determine which content/websites people are actually finding to be valuable by monitoring the amount of times URLs for those sites are shared, liked +1ed etc.
Because of this, it’s becoming more important to allow your websites’ visitors the ability to “like”, share and +1 your pages.
A popular competitive analysis service online (serpIQ) includes the following aspects in it’s “Social factors” score:
– Facebook likes
– Twitter mentions
– Google +1s
– Diggs
– Delicous Bookmarks
– StumbleUpon Stumbles
While it’s not possible to give you a number to aim for with these different metrics, you should try to maximise each number whenever you have the chance.