ZydoSEO - 11:48 pm on Dec 29, 2008 (gmt 0)

Inbound links from relevant sites especially if the anchor text in the hyperlink contains the keywords you wish to rank for would probably have the biggest affect on your rankings.

Unfortunately without knowing anything about your site, it's hard to say whether there are on-page/on-site optimizations that could be made to help improve your rankings. You could try posting your URL on the Google Help Forums to see what type of feedback you get as far as on-page/on-site factors the could be changed to improve your rankings.