Slow in, then speed up a little until you form a bow wave in front of you. Maintain that speed. The difference in pressure will lower the water in the engine compartment and sides. If you can, turn off any fans. They can chip or shatter if they hit water (assuming they are plastic). Secure a tarp over the front end.
For something like a river, you should walk it before just driving in. The center is more than likely going to be the deepest section. People can stand at critical points of the crossing to mark the line or a deeper hole to avoid. If it's fast moving water drive slightly upstream. This will let the water flow more easily around the vehicle instead of running broadside into it.
For electronics you're best bet is dielectric grease for inside the engine bay, and good door seals for the interior. Some seals have a gap at the bottom for drainage. That's great. It can also let water in. If you do a lot of water crossing you could put a dab of silicone to close that gap.
Attach a recovery strap to the rear (or front) end while you're on solid ground. Go in prepared to get stuck and you'll have a faster recovery if you do get stuck. You should also turn on your wipers before entering the water.