You guys probably know all this already, but I play on a pretty old device which is prone to crashing so I've developed a few strategies that seem to work for me:
1) The longer you play the more likely you are to crash, so log out, wait a few minutes, and then log back in before making important attacks in war
2) The more troops you use and the more activity there is on the battlefield, the more likely you are to crash, so if you are still attacking with lots of barrack troops, consider switching to heavy tanks.
3) Turn off sound in your device. Don't know if this one actually works but a lot of people used to suggest it when the game first started