Always check the crossing before you plunge in.
A 4WD should be able to tackle a crossing of around 60cm deep without any problems or preparation, however the approach/departure points, a soft sandy bottom, rocks or a strong current flow can change all that. (NOTE: A stong flow of only 15cm water depth is enough to displace a vehicle, so always be careful)
If just completed a downhill decent, allow 10-15mins for your brakes & diffs to cool before entering the water.
Ensure your engine snorkel does not have any leaks. Spray electrical components with WD40 or similar, loosen the fan belt unless the fan has an auto clutch, and in deep water fit a canvas blind to the front of the vehicle.
Enter the water at a slow steady pace. Low 2nd gear is generally the best. Keep the engine running even if you come to a stop. Avoid having to change gear while in the water at all costs.
Upon exiting the water, stop at the waters edge for a few seconds to allow water to drain back into the crossing from the bow wave & your vehicle, to minimise any erosion occurring to the track.
Don’t forget to dry your brakes out once through the water crossing, and if you were stuck for ANY length of time, check all your oils for contamination.