Help, front derailleur won't shift?

Hi I've got a road bike with SRAM force and the front derailleur won't shift up from the small cog. I've tried tightening up the cable and when I move the shifters I can see the cable tighten and slacken but the derailleur does not move at all, any ideas what to do? I've read every guide on the net and can't find anything - I really want to fix this myself. Thanks