Calling the director to your table has a bad wrap.  This is a GOOD thing!  Think of calling the director as being the same as calling a police officer after a traffic accident.  In both cases it is very reassuring to have a neutral third party available to interpret the rules and prevent fist fights.

Just like the police officer, the director's job is to apply the rules and protect both sides rights. 

Most calls for the director are over very routine situations where a player has made a mistake.  It is important to call the director for virtually all rule infractions because there are usually several alternative remedies.  The director will explain the choices.  Some of these situations are:
 

• Bid out of turn (bidding when it is not your turn)

• Insufficient bid (you make a bid that is lower than that required by the last bid)

• Lead out of turn (someone leads to a trick when it is not their turn)

• Exposed card (a card other than the one meant to be played is exposed)

• Failure to follow suit (a revoke).

There are other situations that require the director that are less obvious.  Most of these involve unauthorized information being conveyed between partners.  These are harder to decide because they are judgment issues and there may be differences of opinion among the players as to what happened.  This makes calling the director even more important.  Some of these situations are:

• Failure to alert a bid that should have been alerted.

• Unusually long hesitation before bidding or passing.

If your opponents call the director, relax, it is not a personal attack (although a very few good players will call the director to intimidate their opponents).  If you were not aware of the rule you are supposed to have violated, tell the director.  Ignorance of the law does not excuse you, but on all but the mechanical errors, the director has a variety of remedies available and his/her judgment of intent can influence the choice.