All right, time for a more detailed answer.
I take apart everything that will easily come loose. If you want clean threads, you'll need to take a small machinists pick and chase the thread from end to end. Wipe clean with a cotton cloth. Clean all O-ring grooves & relube with what the manufacturer specifies (many postings on lube in this section).
If the light has 'extra' body grooves that will accept an O-ring (for increased grip), these can make a nice difference.
Others will mention contact cleaning, and there are posts about that also. And if you want to keep the light ding-free, add a lanyard. The best $10 you'll ever spend, and some day it will keep your prized light from sinking out of sight