To crouch jump in halo 3 you must hit the crouch button (Default R3) at the peak of your jump. This will make your player jump a little bit higher, allowing you to reach certain areas that you could not before. Try using this technique in games to get to higher places that you could not reach before.
Go to a custom game and try crouch jumping on each level and see what locations you can reach that you were not able to before. Once you get the hang of crouch jumping, you can use this in games to have the advantage over the enemy team.
You can also use crouch jumping to clip edges if you are about to fall off of an edge. Hit the crouch button as soon as you are about to hit the ledge and then jump. This technique can save you from falling off of an edge in any map.
You can use the crouch jump technique to “Slide Jump” off of inclines. Jump towards an incline and hit the crouch button and jump as soon as you hit the ground. If done correctly, your player will go much farther than they normally would if you were to jump normally. This technique can help you move around the map faster and avoid enemy fire.
The crouch jump is a wonderful technique to master. Keep practicing until you are comfortable with the crouch jump and then use this technique online or against your friends. You will have a great advantage over the enemy players using this technique