Here’s a simple tip …
Choose a sensitivity between 3-6 and STICK WITH IT. The way your brain works is like this. It adapts and memorizes your sensitivity. Most professional players play between 3-5 senses and the bumper jumper is the most common design used by professionals.
If you always change your direction, your brain will become confused and this can affect your accuracy when aiming. Just because you’re having a bad game day doesn’t mean you should change your mind. Take some time to warm up on a few customs or an easy playlist before playing against hardcore players in Arena or MLG customs.
My rule of thumb when giving lessons on controller setup goes something like this: Sensitivities 1 and 2 are too slow, don’t use them unless you’ve done it too! When you play by default (3), you have no advantage of being faster than your enemies.
I personally play at 4. I was at 5 when I started playing Reach, then I realized that it was a bit too fast for some reason. I missed a couple of shots that I shouldn’t have with the snipe and the DMR. So bringing it down to 4 was good. It’s a bit faster, but still accurate. Anything greater than 6 is less accurate, so I don’t recommend it.
However, in Halo: Reach, if you like to use the jetpack, you will have to grab the bumper (this is where you put your middle finger on the trigger and your index finger on the bumper above it. You can use your index finger to switch weapons with Y or use skills with X as well.
Otherwise, if you like to use the jetpack a lot, you may want to use default or recon as button layouts. My advice in general is to find your comfort zone and not change. Try not to blame your senses for your game, instead go to the movies and see where you can improve.
Thank you, fear your personal Halo trainer.