Rip it up
Alright, let's get to the water. But before we do, let's check if you're a regular-footer (left leg first) or a goofy-footer (right leg first). By this we mean that most boarders have a favorite foot with which they lead. Having the other foot forward feels awkard somewhow.
So get in the wakeboarding stance and imagine yourself being towed. Does it feel more natural to have your left foot forward or your right foot? Remember this, because it will make a world of difference to learning the finer wakeboarding skills.
Remember also that, generally, it's important to not try and get up onto the board too soon as you're being towed. Let the speed of the boat or cable do the hard work. Once your body clears the water surface, that's when you straighten out and put your full weight on the board.
It's the speed of the board that keeps you afloat, so putting all your weight on the board before you've generated enough speed will result in your body sinking back down into the water, at which point the force on the rope will get too much to hold, so you'll let go. You'll then have to start from scratch. Tip: Patience is a virtue here.
Note that there are good ways to fall and bad ways. If you feel you're going to fall, let go of the rope handle and deflect the impact with the water where you can. Falling sideways is better than forwards or backwards.
Lastly, just like any other sports, wakeboarding will tax your body in places you didn't know could be taxed. So a 5 minute stretch/warm-up session is always a good idea. That said, don't be surprised that you're sore pretty much all over the day after your first wakeboarding session. But just realize that it's one more step towards total body fitness and nailing that ultimate trick for all your mates to see.