When playing Halo: Reach, set your sensitivity between three and six, and let your brain adapt to the sensitivity of your controls. Once you have set a particular sensitivity, stick with it as long as you are playing the game. Professional Halo gamers use 3-5 sensitivity while playing the game because this will allow them to gain better controls of their shots.
If you tend to change your sensitivity every time you play the game, your brain will be confused, and will affect the accuracy of your shots. Having a bad game doesn't mean that your sensitivity should be changed. All you have to do is to practice using the same speed and let your brain and fingers adapt to the speed.
Playing with sensitivity 1 or 2 will make your shots a lot slower than most of your enemies, and 3 will make you as fast as they would normally shot. I recommend that you use 4 or 5 to make you a bit faster than most of your opponents, allowing you to fire at them easier. Sensitivity that is set above 6 will make you faster, but trust me, you won't hit a target more than 4 out of tens shots.
Once you feel comfortable with your sensitivity, the next thing that you need to learn is how to improve the accuracy of your shots. When you are firing, avoid multiple times rapidly. One shot should be enough and let the bloom reset, then fire again. This will not only make your shots more accurate but will also help you save bullets that can be used for other enemies.
Trigger happy players are the ones who are seen dead first, and if you want to play Halo: Reach like the professionals does, you need to learn how to relax and wait for the right time to take the perfect shot that will take your enemies down in no time.
