There is a saying 4×4 circles that goes “as slow as possible, as fast as necessary”. Basically, if you are going slowly you are in better control of your vehicle. You are more able to see what is coming up on the trail, pick the right line with less chance of causing damage to the vehicle and trail.
However, sometimes a little speed is necessary to traverse an obstacle, e.g. section of mud, hill climb. The momentum gathered before the obstacle will help carry you through/up. Be careful though, you always need to be in control of your vehicle. More speed would not be appropriate in side incline or other situation where there is a risk you will lose control or damage your vehicle/the trail. In these cases consider using a winch or use bypass if one is available.
When on the trail, always have your vehicle in 4WD (Hi or Lo). Although it may not be necessary, using it impacts less on the environment.
Avoid sudden actions, maintain control over the vehicle at all times. Good “offroading” is about control not brute force.
Keep your thumbs out from inside the steering wheel, if the steering wheel should turn suddenly (from contacting an obstacle), the spokes could break your thumbs.
Never stand downhill of a vehicle and always stand well back of any vehicle in motion.
Do not trust the “Park” setting (automatic) or leaving a vehicle in gear (manual) to hold your vehicle on a hill. Always use your parking brake along with either of the above if you must leave your vehicle on a grade unattended. Try to find a natural chock (i.e. a rock or log) if possible.