Dress appropriately-black pants, white shirt or jacket
Make eye contact with the judge & introduce yourself
Pick a bird you can handle easily-a 5 year old shouldn't try to use a Jersey Giant for Showmanship
Know the breed you're showing including it's history eg: where they originated, uses, other varieties etc
Know poultry nomenclature so that you can name as many body parts as possible [the fleshy proturbance the tail grows from is called the uropigium-that'll impress the judge]
Prepare the bird for showing: make sure it's clean & in good condition
Handle the bird frequently before the show to ensure it's tame so it can be easily handled
Do these things & you'll do well