Here are links to USA Field Hockey and Olympics for solid overviews of the basics of the game. We have also found that this "Mom's Guide" from 2008 still fits the bill.

Field Hockey Basics

Using sticks that are flat on one side and curved on the other, two teams hit and dribble a solid plastic ball down the field and try to shoot past a goalkeeper into a goal cage. Goals can be scored when a shot is taken form within the striking circle; a semi circle extending 16 yards from the goal.

The team with the most goals at the end of the game is declared the winner.

The Game

• Two Halves, 35 minutes in collegiate play and international play, 30 minutes in high school play and 25 minutes in the youth league.
• 11 players per side, including the goal keeper
• The back and side of the cages are 18 inches high.
• Two umpires on the field officiate the match.
• The ball must be passed or dribbled down the field with the flat side of the stick.
• A goal is scored when an attacker strikes the ball into the goal from within the striking circle.
• Players may not shield the ball using their body or stick. All players must have an equal chance to play the ball.

The Equipment

• The Field - The field is 100 yards long and 60 yards wide divided by a center line and a 25-yard line on each side of the field. A striking circle is marked 16 yards out from each goal post. Most games will be played on artificial turf unless otherwise noted.
• The Stick - The stick has a curved head, is rounded on one side and is flat on the left-hand side. The ball can only be touched with the flat side of the stick. The stick is made of composite or hardwood with a minimum weight of 12 ounces and a maximum weight of 28 ounces. Sticks range in lengths based on the height of the player.
• The Ball - The ball, slightly larger than a baseball, weighs between 5 1/2 ounces and 5 3/4 ounces with a circumference of 8 13/16 inches to 9 1/4 inches.
• The Goals - Goal cages of 7 feet high, 12 feet wide and 4 feet deep.

Fouls

A player may not:

• Shield or obstruct the ball from an opponent with the body or stick. All players must have an equal chance to gain control of the ball as it is dribbled or passed down the field.
• Play the ball with the rounded side of the stick.
• Interfere in the game without a stick.
• Charge, hit, shove or trip an opponent.
• Play the ball in a potentially dangerous way.
• Use the foot or leg to support the stick in order to resist the opponent.
• Raise the stick in a dangerous or intimidating manner while approaching, attempting to play or stop the ball.
• Advance the ball by any means other than with the stick.
• Stop or deflect the ball in the air on the ground with any part of the body.
• Hit, hook, hold or interfere with an opponent's stick.

Free Hit

• A free hit is awarded to the non-offending side following an infraction and are usually taken at the spot the foul occurs.
• No player of the opposing team may be within 5 yards of the ball when hit.
• The ball must be stationary and the striker must push, hit it, or start dribbling.
• If the infraction is committed by a defender within the shooting circle, the attacking team is awarded a penalty corner.

Penalty Corner

• In a penalty corner, the ball is placed on the goal line at least 10 yards from the nearest goal post. One attacking player hits the ball to a teammate just outside the striking circle line. A goal cannot be scored until the ball has traveled outside the circle. A shot on goal may be attempted once the ball is played back into the circle. All attackers must be outside the circle before the hit is taken. On defense, a maximum of five defenders may be behind the goal line while the remaining defenders must be positioned beyond the center line.
• If the first shot at goal is a hit (as opposed to a push, flick or scoop), the ball must cross the goal-line, at a height of not more than 460 mm (18 inches – the height of the backboard) before any deflection, for a goal to be scored.
• A penalty corner is awarded for the following offenses:
  • Any breach of the rule by a defender within the circle that would have resulted in a free hit to the attacking team if the breach had occurred outside the circle;
  • Any intentional breach of the rule by the defenders outside the circle but within the 25-yard line;
  • An intentional hit over the goal line by a defender from any part of the field. A penalty stroke is one-on-one, offensive player seven yards in front of the goal vs. goalkeeper on the goal line, with all other players beyond the 25-yard line.
  • A penalty stroke is awarded for any intentional breach by the defenders in the circle or for an unintentional breach by the defenders which prevents a sure goal.

Penalty Stroke

(Although rare in the Youth Leagues - we've included it here for informational purposes)

• A penalty stroke is a one-on-one confrontation between an offensive player seven yards in front of the goal vs. a goalkeeper on the goal line. All other players must stand behind the 25 yard line. The goalkeeper must stand with both feet on the goal line and may not move either foot until the ball has been played. The offensive player may push, flick or scoop the ball from the penalty spot. A penalty stroke is awarded for any intentional breach by the defenders in the circle or for an unintentional breach by the defenders which prevents a sure goal.

16-Yard Hits

• When the attacking team plays the ball over the backline, the defense receives a 16-yard hit. The free hit is taken 16 yards from the spot where the ball crossed the backline.

25-Yard Free Hits

(formally known as long hits)

• The attacking team will be awarded a 25-yard free hit instead of a long hit when a defender unintentionally causes the ball to go across the end line or if the ball glances off the stick/person of a defender in this area and goes across the end line. Play will be re-started with the ball on the 25-yard line that is in line with where it crossed the end line, and all procedures for taking a free hit will apply. The ball must travel 5 yards before being hit into the circle. The attacker with the ball has the option of passing in a backwards or lateral direction or dribbling for 5 yards before hitting into the circle.