RE: Trailing deer. Things you should have with you.
I keep a Coleman lantern in the hunting vehical. Nothing better than it except the sun for following a blood trail.
The #1 thing I would say you must have though is PATIENCE!
The way I see most tracking jobs botched is by not waiting long enough to start... not analyzing what has/is happening.... and rushing down the trail just looking for large pools of blood.... sometimes its just a drop... you have to take your TIME!
The other key thing if you are tracking with two or more people is good communication... you cannot have one person rushing ahead... and another behind acctually tracking. You will step all over each other's feet... and it will be very frustraiting. This goes double when tracking game that is likely not very well hit, and triple when using a firearm. If you don't have everyone where they are supposed to be... its an accident waiting to happen.