Battery life seems to evaporate faster at a conference than anywhere else, so be sure to plug in your phone to get a full charge before you go to sleep each night.
Bring along a backup power source and/or charger during the day, too.
I keep a couple of backup wall chargers and lightning to USB cables, as well as a portable phone charger to keep in my pocket.
A nice convenience when conferences take place in a hotel is that you can book your room there and then go up for an emergency charge, too.
If you’re lucky, there will be a power station at the conference.