Minor Cuts: Wash the cut out with an antiseptic cream or wipe and then put a Band-aid on it.
Major Cuts: Raise the limb above the heart and apply pressure to it. Then wrap it in gauze with a pad on the wound.
Arms: Take two straight sticks that should immobilize the wrist and elbow (four make a more stable splint) and hold them on each side of the arm. Use rope or a sleeping pad to keep them in place and get to a doctor ASAP. The person can spend a night with a broken arm but it is very uncomfortable (I know from experience).
Legs: Splint the leg (see above) so that the sticks go up the entire leg from below the foot to the hip (or as close as possible) If there is someone else with you, send them back to get help. If you are only hiking as a pair, the only thing you can do is to help them to get back by supporting the injured leg (they put their arm around you and you act as their leg).
COOL THE PERSON DOWN slowly. Just pour water on their face and I heard that if you have rubbing alcohol, you can give them a quick sponge bath in it. Don't go and throw them in a lake because that can cause severe shock. You might want to give the person small sips of water as well.
Get the person WARM.Get them in a shelter of any kind. If you have a cabin, turn the heat up to around 90 degrees and give the person WARM drinks. If you aren't so lucky, get in a sleeping bag with them and make as much skin to skin contact (strip them down to their underwear if you have to).
Think about the definition. (Dehydration - the state where the body does not have the amount of water it needs) A.K.A - being thirsty. The symptoms include (among others) head ache, thirst, no sweat, and hunger. JUST DRINK WATER and mix in a little salt too.
Get them out of the back country and to a hospital as soon as possible! They may complain about a sore left arm or chest pains. On cool days they may be sweating a lot.