Links are very important for a sites PR and reputation. Here I would be explaining all I know about links. Anybody can correct me or add anything that I might have missed in comments.
There are two types of links for a site/blog:
1. Inbound: links that point to your site or blog.
2. Outbound: links that point to other sites from your site/blog.
No doubts that inbound links are most important for your sites Ranking but importance of quality outbound links cannot be ignored at the same time.
If your blog or site is relatively new, you should start with good outbound links in relevant sections of your site. I have seen an increase in my sites listing with good outbound links, on some of my blogs initially.
To build initial inbound links, comments and forums are a good starting point.
One such forum where you can start with link building is Digital Point Forum
Also blog catalogs and link directories are a good starting point.
If you are building links to your blogs then you can also consider Technorati and Digg to register and network with people.
