Radio controlled model airplanes provide a taste of flying that you will cherish forever. But to keep it fun, it's worthwhile to keep a few safety tips in mind.
First - always make sure *before* you turn on your radio that no one else is using your frequency, on the ground or otherwise. If you power up your radio and it is on the same channel as another RC flyer, you're likely to knock their plane out of the sky - destroying the airplane, and putting people and property in harm's way.
Second - make sure you're properly fueled up. If you're gas, make sure the tank is full. If you're electric, make sure the batteries are charged. If your plane falls out of the sky for lack of fuel, it can become a dangerous air to ground missile.
Related Topics:
Third - Preflight your airplane. Check control surfaces and internal mechanics. I've made this mistake before, after a particularly rough landing, one of my rods shook loose, rendering my right aileron inoperable. I had no problem getting airborne, but getting that airplane back on the ground was an exercise I never want to experience again.
Finally, if you're brand new to the sport of RC flying, I highly recommend practicing with one of the many available computer simulators. You'll crash and burn your virtual aircraft with no harm to person or property.