Those would be my starting points Skye
Firstly, start by finding directories for the industry your in. Submit your sites details to all you are able to find. You would be surprised at how many you may find!
Secondly, find sites similar to yours and ask for reciprocal links (i link to you, you link to me) but instead of swapping your homepages, try deeplinking to pages that may interest your users and ask them to do the same
Thirdly, buy links from the players in your industry. Maajor caution must be advised though.
Those would be my starting points