Halo three is a game played by many, but mastered by few. Here are some general tips to help you reach that next level.
Crouch walking will not appear on the radar
If you crouch at the right time during a jump, you can reach places that are hard to get to with a normal jump
Being good with grenades is the best way to get better. Use them as one of your first options.
With a ghost, pretend like you're going to run the enemy and stop. The enemy will likely jump and then you can boost into them on their way down.
A charged plasma pistol shot will temporarily stall an oncoming vehicle
Vehicles are more resistant to gunfire so aim at the exposed driver
When both players melee at the same time, the person with the least damage will get the melee off
Always look for red x's to see where teammates have died
Plasma weapons shoot farther with more accuracy but are slower than human weapons. Plasmas are also better at taking shields down but worse at taking health down
When you are carrying power weapons like the shotgun, sometimes it is good to be holding a lesser weapon to feign weakness. When an enemy sees this, he/she will like confront you at which point the shotgun can come out.
Even if you may not be able to kill them, always shoot at enemies when you see them. This may help out a teammate if they run into that enemy soon after. The obvious exception to this fact is when shooting would give away your position.
Sniping
Head shots are great but not always necessary. Two body shots will get the kill.
Holding down the right stick will go back a zoom level
It's easier to aim by strafing rather than moving the right stick
Swords and Gravity Hammer
A melee is faster than pressing the right trigger. In a sword battle, a melee versus a normal sword lunge will always win. Be careful though, the melee should only be used in close combat because it does not lunge as far.
The gravity hammer can attack through surfaces walls, glass, and invisible shields
Equipment
Place trip mines on the landing spot of a man-cannon
You can shoot through the bubble shield while most of you is still inside (making you invulnerable to attack)
Power drainers are particularly good in team objective games such as king of the hill and capture the flag because they flush the opposing team out of the area when they run away from the drain
The power drain, trip mine, and gravity lift are all excellent equipment to drop in front of an oncoming vehicle
