You might consider some of the following ideas;
'coupons' for -what? - maybe 15 minute intervals of professional help. maybe give 4 or more as an incentive for a membership. They expire every 2 months, but members get 2 new ones every month. Coupons could also be used for 'sick-days' when you can't make it in to work on the car. maybe Walk-ins/non-members get bumped down the waiting list if a member needs a bay.Non-memembers buy pro assistance. maybe a high 'minimum for the first 15 minutes, then a reduced amount for every 15 after the first.
video surveillance. might cut down a little on disappearing tools, might be helpful if an accident occurs.
consider having customers watch a short safety video. Check with insurance company if it might save you some money.
How to decide when to 'evict' someone's car. 4 consecutive weekdays of no work done or 3 days if a Sat or Sun is one of the no-shows? park it? tow it after X days? check into 'abandoned car' rules and liens.
Ask local police if they need vin numbers to check for stolen vehicles? maybe just vehicles that look like they are being parted out?
check into 'sponsorship' . maybe some tool, lubricant or parts company would furnish free/discounted products if you use their stuff and put up some banners.
get a 'roach-coach'/food truck to stop by. (kick-back?)
get a mobile detailing service lined up. (kick back?)
sponsor an occasional basic maintenance Powder-Puff seminar, First Car seminar for ladies and teens.
Have a coupla car-port bays for quick stuff(battery, belt swaps,plug changes etc.) maybe some intermediate covered bays with drains/w'ever where ramps are allowed for fluid changes.
a lot just depends on what you feel your typical customer is like, and how accomodating you want to be for a customer with more extensive needs. For instance, ,right now I'm trying to change a front hub bearing assembly on my daighter's car and it's taking be MUCH longer than I expected. But other things like an oil change or pad-slapping the brakes, might never take more than an hour or 2. It's kinda like a bell curve. Someone that needs a spot for less than half a day, shouldn't get gouged. Someone needing a spot for a month shouldn't either(that's steady, guaranteed money - maybe after 2 weeks though, the price starts creeping up to encourage getting the car outta there?). someone taking up a spot for several days - well, you need to encourage people to clear up space for the next paying customer. Maybe only allow long-term rental to one spot. keep a waiting list for it or find some way to auction it off????
maybe develop a way for people to earn time when they help other folks. Like collecting 'Thumbs Up' from other users. Or, that may very well lead to a lot of liability and perhaps customers should be warned to refrain from offering help to other patrons ?????
just some odd thoughts I had about it.