First thing to consider; are you inside the truck or outside? 

If you're outside the vehicle: How many people do you have? If more than 2, position someone downstream of the vehicle with a throwbag to rescue rescuers. 

Determine if the vehicle is stable. If it's not, stabilize it. If it's deeper than 1/4 down from the top of the tires, it may wash away while you're trying to stabilize it. Beware of this. The stronger the current the more likely it is that the vehicle will break loose from the bottom and roll. See the note on rolling, below. 

If there is current against a window, don't break that window. You'll probably drown the victim. Breaking a window of a sealed passenger compartment will sometimes result in the other windows breaking -- the other windows can be partially supported by the air in the passenger compartment. It's not uncommon to have 2-3lbs of pressure inside the cab, and to have the cab or passenger compartment violently flood after a window has been broken. Be aware of this and have a plan to deal with it. 

When you are removing passengers, be aware that you are changing the center of gravity for the entire vehicle. Replace the weight removed with a like amount of mass (rocks or sandbags work well) to help guard against the vehicle rolling. 

If the vehicle starts to roll in the current while there are still people in it it is unlikely that they will be rescued. They'll be recovered; but not rescued. Encourage the occupants to get out ASAP if the vehicle starts to roll. 

If you are inside a vehicle that goes into the water: If it's deep water (deeper than the car is tall) GET OUT! GET OUT! The car will descend to the bottom and hit the bottom with the end that is closest to the engine. That is, most vehicles will hit in the front, but VW bugs will hit backwards. It will then fall so that the roof is down, and if there is anything but a hard bottom (like sand, mud, silt...) the roof of the passenger compartment will be completely buried, entombing the passengers. If you are inside the vehicle and can't use the doors, kick out a window or the windshield. If you do not succeed you will probably not survive. [SRT Rescue Technician 1 course gets this description from examining accident reports and from having driving 20 cars and trucks of all models into a lake from a pier. They ALL acted this way] 

If it's shallow water, open a door on the upstream side and be prepared to abandon ship. If the water is higher than the center of the wheels and there is a current it is probable that you will roll. If you don't get the door open before you get completely down you will not be able to open the door -- the current will hold it shut. Do NOT try to exit on the downstream side -- you're risking the vehicle rolling and pinning you or having the vehicle hit a downstream obstacle and pinning you. 

Don't drive into water deeper than your axles.