Purpose
The football helmet is only and only a protective gear. It is not an offensive weapon.
It’s only purpose should be to protect the player’s head and face. The player should never initiate the contact with the opposing player with his football helmet.
Correct fit
A football helmet is just as good as it fits the player.
It should not be too tight, that is it should not be uncomfortable or squeeze the head at any point. (It should not leave any visible wearing marks from just wearing the helmet)
On the other hand it should not be too loose:
It should not move when the player is running.
And the football helmet should be still in place after ‘normal contact’ so that the player is not looking out of the earhole after almost any contact.
Treatment
If you have to paint the football helmet make sure you only use paint that’s not aggressive to the plastic material of the football helmet’s shell. There are paints that would weaken the shell of the football helmet so it is not really protective anymore
Throwing the helmet is not only unsportsmanlike it also might affect the usability of the helmet because hits to the helmet when worn might cause small – at first invisible – cracks in the shell of the football helmet and therefore make it actually unusable.
The same is also true for sitting on the football helmet.