Absolutely nothing,
especially for newbies. The genuine Joyetech batts and twists have some of the best short circuit, etc. protection there is. Due to the protection circuitry in the battery, the battery is simply going to shut down in the event of a short.
(unlike a purely mechanical mod).
Anyone using a mechanical mod should of course, go to the ECF library and learn about batteries and battery safety.
I stick this kind of post in every so often as a reminder. I know there are a lot of new vapers and everyone who uses lithium batteries needs to understand battery safety, esp. if using a purely mechanical mod with no protection circuitry. Buy the best charger and batteries you can afford, don't over-discharge your batteries, don't leave stuff on charger overnight, and understand the amp limits of the batteries you are using, etc. Hopefully you have a multimeter so you can make sure the delivery device you're putting on your mechanical mod isn't shorted out to begin with, etc.
Besides the ECF Library, this is a good article, I stole the link from Baditude, but I'm sure he won't mind me using it as it really helps newbies learn about battery, charger, and mod safety.
Mechanical Mod Proper Usage Guide