a short happens when a current carring conductor(a wire in most cases) leaks its current into anoter condutor or simiconductor.. ie in dc you have 2 current carring conductors the + and - or hot and common.. the - is called common because there all bonded and use the same source(the vehciles chassie/body) so anytime the positive hits the negitive wethier it be the frame on the - wire it creates leakage and or a very low resistance to current flow so all the current is flowing at that one point...
what i want you to do is put you lights on and pull fuses till they go off... you can do this with the car off, but not for too long you don't want to kill your battery...i would do it with the car on.. then once you find that fuse(the one that kills the lights) with it out lights off blow the horn... if there on hte same fuse chances are its faulty wiring.. also like others said dfisrt a formost check all you connections to make sure there very good... do this before you try to trouble shot you light circuit...
also make sure when you pull a fuse and it doesn't kill the lights you replace it before pulling another...