I would start by creating an inventory of your linkable assets and taking a peek at your existing natural links in Google Webmaster Tools. Try to understand why those who already chose to give you a link did so and try to create more cause for linking through content and value on your site.
Once that's out of the way you can move onto finding references of your brand online and create links where they don't exist and they should:
- Mentions of your brand
- Your logo (try tool called tineye for that)
- You URL (but not linked)
Also cover all meaningful directories relevant to your niche and location.
Another great way to get links is by thinking about your business relationships (suppliers, customers, office space, partners...etc). Here you can gain good value through nice contextual linking situation or a testimonial.
Occasional article, blog post/guest blogging, blog commenting can help - though I would advise against use of your key term instead of name in blog comments. That's something spammers tend to do.
If you run out of ideas you can always take a look at your competitor's links using tools such as:
- Majestic SEO
- Linkscape
Or you can use free tools including Yahoo and Google's own link: command.
For more try to read material written by http://ontolo.com/link-building-tools and informatoin already available on SEOMoz http://www.seomoz.org/blog/link-building-101-the-almost-complete-link-guide
Good luck!