Before starting any water crossing always assess the situation and know your fourbie's limits.
Always make sure it is safe to cross where you are about to cross and the lead vehicle should always go through driver-only. Getting one person safely out of the vehicle is much easier than getting a whole family out.
If the water is moving and higher than your undercarriage. Keep in mind that the force of the water has a much greater chance of washing your 4x4 away. The better your cab is sealed, the more likely you are to float. Make sure your tyre pressure is down, not only will it reduce float but it will also help with more grip and less likely to pop a tyre on unknown debris.
Know where your air intake is. Don't ever go deeper than your air intake otherwise you will end up with an engine full of water. This is why it is always a good idea to install a snorkel if you don't already have one.
Before crossing spray your electrics with a good water dispersant such as WD-40 or a lanolin-based product. If you have a points ignition system put a smear of grease on the lip of the distributor cap to help keep water out of the distributor.
If you aren't confident watch someone else do it successfully first and follow their track. Make sure there is only ever one person in the water at any time and wait for the exit point to be completely clear before crossing.
If you can't see the bottom, walk the crossing first. Make sure there are no underwater drop-offs or debris that may damage your vehicle or leave you stuck in the water.
Know which gear is best for the situation and your vehicle to cross in. If in doubt use 2nd gear low range. Keep a constant speed to maintain the bow-wave in front of you, the bow-wave will help keep the water out of your engine bay.
If you a concerned about too much water getting into your engine bay and electrics wrap a tarp around your bullbar.
If your engine is hot, consider disconnecting your thermo fans or turn your vehicle off and let it cool down.
Always keep your windows open in case of emergencies in the water, even if the water is only halfway up the door. It is unlikely you will be able to open them due to the water pressure. On the upstream side of the car, the pressure will be greater and you may not be able to get out in a hurry.
When crossing, depending on the current and location of entry and exit points, you will most likely need to steer upstream to go straight.
River depths and current can change in a moment depending on weather and conditions further upstream. Toward the end of winter, when snow is melting and after rain events, what you may have crossed successfully once may become treacherous within the hour.
River and water crossing are one of the most dangerous things you can do in your four-wheel drive so if you aren't confident in getting through it successfully try and find another way around or let the experienced lead go through and winch or tow you through to the other side.
IF IN DOUBT DONT RISK IT.