problem with horn on 2003 ZX3

this started happening right after i got the car. lucky me. :)

for a while my horn would work sometimes and now it doesnt work at all. if i push the horn on the steering wheel it wont work and it wont honk when i lock the doors. can someone give me a direction to look in for solving this problem?

Thanks.

Check to see if the horn has power.
Check the horn itself.
Check the grounds for the horn.