Do the ABCD bike safety inspection before each ride: A=Air Pressure. Check the air pressure on your tire. B=Brakes. Check to make sure your brakes grab to the tires and stop. C=Chain and Crank. Make sure your chain is on the gear flywheel and the crank spins properly. D=Drop. Drop your bike 3 or4 inches off the ground. If something makes a bad noise or falls off, you should look into that part.
Check your quick releases and make sure they are tight. This will prevent your wheels from falling off during your ride.