The Bright Angel Trail is 10 miles long. Water is available at Indian Gardens, roughly the halfway point. Both trails cover nearly a mile in elevation change. Plan to dress in layers and avoid cotton. Backpacks should fit properly and be large enough to accommodate what you need for the length of your trip.
Boots are important in the Canyon - and lots of socks.
Moleskin, which prevents hot spots from becoming blisters, should be part of a first-aid kit. The gloves can be stuffed into pockets when not needed. Avoid foods high in protein or fat, which are harder to digest and can unsettle the stomach while hiking. Bring resealable plastic bags for trash. Plan to carry out what you carry in.