Would it help if I added some fluff or something? It's in a pretty quite area but they never seem to come.
i hear you have to leave them 12 months before they start using them, so dont worry bout not gettin any visiters straight away =)
Is this a nesting box? What size is the hole? Where is it located? I've had birds start to occupy a nest box within hours after putting it up. Target species in settings that they are known to take advantage of. You situate nest boxes for certain species of ducks, so many feet up from the surface of a body of water. Also feeders and cover help attract birds to your area.
What species are you trying to attract? That matters a lot, as does your geography. It can take a long time for a box in a borderline location to be occupied, but if you place them right, you'll generally see occupants in the first spring. Have you contacted your local fish and game for local bird groups that can advise you? If you're in town, see if you've got a Wild Birds Unlimited store- they also usually know who to ask locally.