"corehaven method"
Find your 360° sensitivity
you need to be able to do a full 360° rotation on the space of your mouse pad
if you have less DPI, you need more mousepad ;)
Take it times 1.5 and divide by 2
e.g. starting with 800 for a full rotation, you try 400 and 1200
Test both sensitivities
If lower is better, divide by 2, if higher, take times 1.5
from then on: add them together and divide by 2
cross the bad sensitivity
add avg+good sens together = new high
Usually a good starting point is ingame sensitivity 1.0 with DPIs 400, 800, 1200 or 1600.
You should use the lowest sensitivity you feel comfortable with to prevent "overaim", meaning that you don't stop at your enemy but rotate slightly farther than you needed to.