From Law 8: Coin Toss



USSF Advice to Referees (08/08/12):

Law 8 - The Start and Restart of Play

8.1 COIN TOSS
The decision made by the team winning the toss is only which end of the field to defend attack; the other team takes the kick-off. When extra time is played, the coin toss again decides only which end the team winning the toss will defend attack in the first extra period of play. The team that wins the toss at extra time also kicks off to start the second period of extra time. A separate coin toss is required for kicks from the penalty mark; however, in this case, the team whose captain wins the toss decides whether to take the first or which goal to defend  the second kick.