For us and our TT, here is what we do before each trip or some days before (depending):
1. air pressure in tires okay and are lugs tight?
2. do I need propane refill?
3. taillights, brake lights work?
4. fridge, heater, AC all work?
5. water pump OK? And, once system pressurized, do i have leaks?
6. did critters get in since last we camped?
7. TT battery okay and charged?
8. other items as needed
Longer term maintenance items (not complete list) include:
1. repacking wheel bearings
2. winterizing / de-winterizing
3. other items as needed
Others will have different views but to me, the general checks before a trip (above list) is our best bet to an issue free trip.