Just like the schoolyard game of your childhood, capture the flag involves two teams in an all out battle to capture a flag from the other team. Each team gets a flag, which is placed on the far side of the playing field and hidden. The next part of the game involves teams moving into enemy territory and trying to capture the enemy's flag.
The best tactic is dividing the team into fireteams of two to three people and each take a different route. This divides the enemy's attention and causes a distraction.