Contacts more than anything matty - get a couple of prints out at a "good price" on the proviso that people drop in a good word for you and it seems to get the ball rolling.
Most of my print sales are to people, as opposed to shops or companies - an interesting market is people moving into a new house or flat, who want to inject some life into it all - word travels some, and then you have x couple who saw the prints on y couples walls and wouldn't mind some for themselves, albeit perhaps different shots.
The first one is up in two café's though - I sold it cheap to one café, the owner of another saw it, and wanted the exact same print - I sold it to him at full whack.
I do try to get rudimentary advertising about where I can, but none of it seems to really do an awful lot - I would say 99% of my sales come from word of mouth, which is one of the reasons I always do my best to ensure my customers are happy with what they have!