Protect your batteries. Keep them in a case that prevents them from coming in contact with things like loose change in your pocket. Better safe than sorry.
I don't know how useful this information really is but the FDA put together some tips on how to avoid having your vape battery explode lol.
FDA Tips: Tips to Help Avoid "Vape" Battery Explosions
Only way to extinguish a metal fire is with either a Class D extinguisher or a bucket of sand to smother it. And Li batteries fall in that catagory so a plain A, B, C extinguisher most of us have in the house/kitchen (or really should, I know from prior experience) won't help you at all.