
Have a read of the first post on the Breeding forum of this site. Your dog will need to have a hipscore (perfomed after 12 months of age) no higher than the breed average and have successfully passed any other breed-specific checks for hereditary problems.
Advertising is done by you taking him to where bitch owners see him and judge him for themselves - that means either shows or (as he's a gundog) field trials. If he does well, they'll ask if they can use him. Then you'll have to research the pedigrees of the bitches to see if theirs are strong where his is weak (and every single dog has faults, even champions!).