The Fireteam
A fireteam consists of three to six men. One member is usually armed with a light machine gun and one is the team leader. In some formations there is also a grenadier with a grenade launcher. In US Marine units the grenadier is usually the fireteam leader, in some Army units the grenadier is just a team member.
A fireteam is usually the smallest unit sent out on patrol and the team relies more on stealth than combat power because of its small size.
A well balanced combat unit, fireteams are designed to be versatile. The fireteam revolves around the light machine gun. The team leader insures the machine gun is positioned where it can do the most damage to the enemy. If the machine gun cannot fire at an enemy because of a dip in the land, a crater where the enemy is hiding or whatever, the grenadier can lob grenades into the enemy's location. If the enemy is protected or some reason from the low angle arc of the grenadier the machine gun can provide covering fire while one of the riflemen gets closer and throws a grenade or places a demo charge.
Because machine gunners are a primary target for the enemy the machine gunner is kept as safe as possible (like he does not usually lead an attack). Also, if the machine gunner is injured or killed, the next (or closest) senior man picks up the machine gun and becomes the new gunner. Regardless of casualties, the machine gun is the most important part of a fireteam. Without the machine gun the fireteam is a whole lot less effective.
The machine gun is also manned at all times. If a machine gunner is digging a hole, eating or relieving himself he gives the machine gun to someone else and takes their weapon until he is done.
In addition to carrying their own ammunition, each member of the fireteam usually carries extra ammo for the machine gun. Rocket launchers (like the LAW and AT-4) dramatically increase the effectiveness of a fireteam. A long range radio also increases the lethality of the fireteam ten fold because if they can't destroy it with their already considerable firepower, they can call in artillery, mortars, strike aircraft or reinforcements.
The Firefight
In battle a fireteam, when properly trained and led, is incredibly effective. Armed with machine guns, grenade launchers, anti-tank rockets, hand grenades and a radio a fireteam is the most lethal, single unit on the battle field.
When a firefight begins everyone takes cover and fires at the enemy. The fireteam leader directs the machine gunner to the best position and directs the fireteam to concentrate fire on certain targets (like enemy machine guns or leaders).
If a target cannot be killed by direct fire weapons, the grenadier opens fire.
If the enemy loses the advantage, the fireteam leader may direct his team to advance on the enemy. Depending on the amount of return fire his team is receiving, he may move his team individually or in pairs. He might even move everyone except the machine gunner and once everyone has moved, then he will move his machine gunner (or vice versa).
Basically, anybody moving is supported by accurate fire, whether the person moving is a single person or several, he has people suppressing the enemy while he finds a better position, reloads or carries out some other combat related task.
Unless the fireteam leader retains control over movement, (not an easy task!) movement is like it is for battleteams and individuals.
On Patrol
Each member of a patrolling fireteam adheres to the basics of individual and battleteam patrolling. In addition to those basics, fireteams move in formations. Each formation has a different purpose and is designated anticipating enemy contact. Since it is tiring to move from cover to cover, getting up and down, formations are used. It should be noted that although a formation looks good on paper (or screen) it is not easy to maintain any formation because warriors have to go around objects and don't pay perfect attention to the formation. Also, when the firing starts most units deploy in a line facing the enemy so everyone can fire freely at the enemy without endangering a friend. Every team leader and squad leader is different so there will be variations according to the whim of the leader. In larger formations more can change so all machine gunners are not on one side, ect. In general, the team leader places himself where he can best see what is happening and so control the unit.