Bing's official blog posted an article about link building [bing.com] that discusses a number of issues. It's a far ranging article that includes a little about how Bing analyzes links in addition to recommendations of how to acquire links. Some of these tips make sense although some left me scratching my head. You judge for yourself. :P

Here are some interesting points, but I suggest you read the entire article. In this part, Bing encourages webmasters to contact one another, something I think Google has stopped recommending on their official webmaster pages.

You contact webmasters of other, related websites and let them know your site exists... That, my friend, is the essence of link building.

A word about relevance and rank scoring:

Relevance is important to end users... If there is a clear disconnect, the value of that inbound link is significantly diminished, if not completely disregarded.

A non-green-pixel definition of an authority site for those who are hooked on Google's toolbar:

Authority sites
Sites that possess great content, that have a history in their space, that have earned tons of relevant, inbound links - basically, the sites who are authorities in their field - are considered authoritative sites.

Things to watch out for when link building:

Going unnatural
The number of inbound links suddenly increases by orders of magnitude in a short period of time

Many inbound links coming from irrelevant blog comments and/or from unrelated sites

Using hidden links in your pages

Receiving inbound links from paid link farms, link exchanges, or known "bad neighborhoods" on the Web

Linking out to known web spam sites

This tidbit about a negative page rank is interesting:

When probable manipulation is detected, a spam rank factor is applied to a site...

There is a full list of link building methods. Here is a small sampling. Read the blog post though because there is a lot more:

Publish expert articles to online article directories

Participate in relevant blogs and forums and refer back to your site's content when applicable...

Use social media sites such as Twitter, Facebook, and LinkedIn to connect to industry influencers to establish contacts, some of whom may connect back to you (be sure you have your profiles set up with links back to your website first)

Join and participate in relevant industry associations and especially in their online forums