Mix up your opponents with stutter-step strafing.
As much heat as Halo gets for its sluggish movement, it still has one of the quickest strafing systems in the first-person shooter genre. Because of that, the stutter-step has been a staple for dueling players with even the best aim. The strafing is so fast in Halo, so make sure you do everything you can to master moving side quickly without messing up your own aim in duels.