Weather you're there just to relax and want to be 'deck fluff' or you'd like to learn enough to eventually skipper a boat yourself it starts with basic stuff.  (Well, duh, like we're going to start you with rebuilding an engine!)  Just like government, sailors have their own terminology.  (Fortunately, no tax money was spent to develop sailing terms.) 

Certainly, the most important term you need to remember is how to address the captain of the vessel.  Particularly if he's the owner.  (You wanna get invited back, don't you?)  You will probably know his name, unless he's in the witness protection program or hiding from his parole officer.  But better results can usually be obtained by using terms like: Your highness, your lordship, captain wonderful, master and commander, incredible hunk, super sailor dude, etc., ad nauseum.  The real trick is to say them without sounding sarcastic; in other words, fake some sincerity.

Parts of the boat:

Bow (That's bow, as in take one; not tie one.)     The front part of the boat (the pointy end, for you technically challenged.)

Stern        The rear part of the boat.

Port         Means the left.  Could be the left side of the boat or a direction; as in, "turn to port".

Starboard      Right, opposite of port.

To keep port and starboard straight just remember that both 'port' and 'left' have 4 letters.  Also, 'left and port' are shorter words than 'right' and 'starboard'.

Rudder      The steery thing in the water that controls the direction of the boat.

Tiller         The stick connected to the rudder that you move to turn the rudder and the boat.

Wheel       Takes the place of the tiller on larger boats.  (Gives better leverage.)

Mast       Tall, vertical (hopefully) stick in the center of the boat to which the mainsail is attached. 

Boom     Horizontal stick attached to the mast to which the foot (bottom) of the mainsail is attached.

Mainsheet    Line (rope) that controls the mainsail.

Foresail      Sail at the front of the boat.  We usually use a jib, but there are others.  What you don't want to hear is, "break out     the stormsail"! ;-)