Congratulations, X. You're certainly allowed to live in it in the driveway for awhile! We sure did.
Seriously, it's important to spend about a week in it. First, make sure the break-away brake pin is in. Wrap the cable back over the switch and around the jack so it can't accidentally get pulled.
Sanitize the fresh water system and fill the fresh tank. Put about 4-5 gallons of water in the black tank to prevent the dreaded black mountain.
Turn on the pump, make sure the water heater is full (no air in the hot lines) and fire it up once to make sure it works. Shut it off until about 1/2 hour or so before you need hot water.
Light each of the stove burners. Once that's done, light the pilot light in the oven, if so equipped. Set it on 350 and make sure the whole burner lights up. Then shut the oven control off.
Fire up the refrigerator on gas. Fill up some ice cube trays and put them in the freezer. Put a few cases of pop and/or beer in the refrigerator. Make sure it freezes/cools them down on gas.
Turn off the refrigerator temporarily, then shut off the gas at the propane tanks. Wait a couple of hours and go back and try to light one of the stove burners. If there are no leaks in the gas system, the burner should light and burn for a little while until the gas pressure drops. If there are leaks, you'll have no pressure at the burner and it won't light and burn. Turn the gas and the refrigerator back on Auto.
Get a good 30A extension cord, if necessary, and a 30A female to 15A male adapter and plug the trailer into the house.
Switch the refrigerator over to AC. Dump the ice from the trays into a ziplock bag, and put that and refilled trays into the freezer. Leave the refrigerator running on AC for awhile and make sure the trays freeze and the ice in the baggie doesn't melt, but stays in cube form.
Pull the battery caps and make sure there's sufficient water in them. You'll be charging them while plugged into the house AC.
Check all the 12V
lights and fans, and the radio and water pump. Take a 120VAC outlet tester around to all the 120V outlets and make sure they are wired correctly.
If you have something that plugs into a 12VDC cigarette lighter outlet, try it in them, otherwise measure their voltage with a meter and make sure they're live.
Bring a TV out to the trailer and hook it up to the outlet(s) making sure you know how to use the antenna. Don't forget to turn its amplifier off when not using it.
Try the microwave oven, if so equipped, with a cup of water.
Each of you should heat up a tank of water and take a shower. This will give you a good idea of how much (or little) hot water you have, as well as how hot the water gets. Don't quote me on this, but you can/should dump the grey water on the ground, to get a feel for dumping. A little soapy water isn't going to hurt anything.
Check the air pressure in the tires and the torque on the lug nuts.... now and every 50 miles for the next 100 miles.
You'll learn a LOT in a few days of living in the trailer in the driveway!