Empty water bottle
When you pack you carry-on luggage rember to pack an empty water bottle this way you avoid paying huge mark-ups for bottled water at the airport, after the checkpoint you fill up at a water fountain. Because you bottle is empty it will go through security just fine.
Photo of your parking spot
If you snap a photo of you parking spot before heading to the terminal, (be sure to include signage identifying your location level, aisle, etc.). At some airports the garage or terminal number is not obvious on the signage, so you may need to remember which garage you were in.