One of the more common reasons for failing the drive test is due to improperly yielding in traffic. The following video from the igottadrive.com video library discusses proper yielding which can help drivers avoid one of the major reasons for failing the drive test.
From the video we learn that properly yielding on an unprotected left turn is one of the main reasons for failing the drive test. An unprotected left turn occurs at an intersection where there is no traffic light to signal the turn. The critical item is to understand that yielding is defined as "not causing any other drivers to change speed or direction due to your actions as a driver". So in order to properly yield, engage turn signal, get into a position where oncoming traffic can be seen, stop until there is a gap large enough to not cause oncoming traffic to "change speed or direction", and then proceed to make the left hand turn.
Practicing unprotected left turns and watching this video prior to the drive test will increase your chances of passing the first time.