For water crossings keep slow and steady momentum so you have a bow wake in front of your truck. Instead of crossing perpendicular to the flow of the stream, cross so you're going slightly upstream. Don't stop in the water. Try to avoid anything deeper than halfway up your wheels. Only cross streams at designated crossings.
For mud, avoid it if you can. Nothing wrecks a truck faster than mud that gets into moving parts. If you can't avoid the mud and you get stuck, instead of spinning your tires and throwing mud everywhere while only digging yourself in deeper get another vehicle to recover you. If you have street tires (tires that aren't AT, MT, etc.) you WILL get stuck in mud. In fact you might be surprised at how little mud it takes to get stuck in even with AT or MT tires. I hate mud so much that I don't go off road during runoff or if it's been raining a lot.
If you aren't sure how deep water or mud is, stop, get out, take a look, grab a stick and poke until you hit bottom. Never be ashamed to pull the plug and turn around. Getting hydrolocked will ruin your day pretty fast.
But most of all have fun and TREAD LIGHTLY!