Take your valuables - Always try to take with you or conceal all your personal and valuable items when you park, such as house keys, loose change, EZ Pass, phone charger, and documents. Garages do typically have a strict no-tolerance policy when it comes to employee theft, but nearly every garage's claim check clearly states that "garages are not responsible for items left in cars".
Inspect your car - Walk around your car with the valet to confirm any existing damage that you may have. This documentation gives you recourse if you find any damage when you retrieve your car. Garages that inspect cars for damage are noted in this book by "Damage Inspection".
Know your numbers - Make sure you write down the exact address and phone number of the garage on your claim check. Then put the claim check where you won't forget it.
Bumper guards - Some garages provide these guards for a small fee, or you can purchase your own.