Avoid hard chewing, as it tends to overdevelop. Make sure to have good tongue posture too, but it also depends because if it is natural skeletal structure then you may not be able to change without surgery. Also another factor, it is still growing if you're a teenager and tends to stabilize around age 21.
(vote solution pls!)
Edit, forgot to add this:
If it does not change in adulthood/when it should be stabilizing, it is likely surgery is the only option. Don't mess with it right now to make sure nothing has negative impacts.