How do you teach new people to wakeboard?

Andy is right on the money. I ran water sports at kids summer camps for 2 summers and all I taught my guys to tell them:
1. arms straight
2. knees bent
3. knuckles on the board
let the boat do all the work
0% didn't get up
never had them put arms outside of legs, will give that a try.
Don't confuse them with handle position once up or what foot forward, it is just too much all at once.

Step 2 once they can get up:
handle to lead hip or let go with back hand if comfortable, if they don't skateboard or snowboard and don't know if they are goofy or regular as them what foot they would put forward if they were going to slide on a wood floor with socks on

step 3:
Now that they are hooked tell them that the first time is free and now they have to bring gas/money next time!