Basic Terminology

Tee markers (Rule 11-2)

When teeing off on a hole, the ball must be behind the tee markers. (Draw an imaginary line between the two markers and tee your ball behind that line.)

As it lies (Rule 13)

Play the ball as it lies. This means you may not improve the way the ball is sitting. If you are on the green, you may mark and pick up your ball to clean it, but while anywhere else on the course, you must play the ball as it lies. See the USGA rule book for special circumstances like winter rules, obstructions, standing water, etc.

Away (Rule 10)

The ball farthest from the hole is the one that is played first. The term is "away." Example: "Sara, you are away, so go ahead and play first." The person with the lowest score for the hole has "the honors," and plays first on the next hole. Many times in social settings, golfers play out of turn to speed play. In a social environment this is OK as long as it is safe to do so.

Bunkers (Sand traps) (Rule 13-4/b)

If your ball lands in the bunker, remember to rake it after you have played your shot. The groups behind you will appreciate this. Since this is a hazard, you cannot rake it before you play out of it, and you cannot ground your club prior to the swing. Practice swings are okay, as long as you do not contact the sand.

Out of bounds (OB) (Rule 27-1)

If you hit your ball OB, there is a one-stroke penalty, and you must hit another ball from the exact same place you hit your first ball. If you are not sure if the ball is OB, hit a "Provisional Ball" just in case. If you determine that the first ball is OB, then you continue on and play with the Provisional Ball. If the first ball is not OB, you must play it.
Water hazards (Rule 26)

If you hit your ball into a water hazard, you may play it (could be messy), or play another ball from where you just hit (with a one-stroke penalty). It is important to see how the hazard is marked if there are red lines or stakes, another option is to drop a ball where the original ball entered the hazard, add a one-stroke penalty and continue play. 
Putting green (Rule 16)

When on the green, never walk across another player's line of putt. The line of putt is an imaginary line that the ball will most likely follow towards the hole. The imprint that your feet leave on the green can alter the path of the ball. Always step over the line of the putt or around it.

Have fun

Golf is a great game, so have fun with it and whenever possible, leave the golf course in the same shape that you found it.

Rub of the Green (Rule 19-1)

A “rub of the green” occurs when a ball in motion is accidentally deflected or stopped by any outside agency.