I agree on the research. I usually have newbies start with the Birnbaums guide - it isn't the most in depth, it isn't the best - but its the most user friendly, it isn't intimidating, it has lots of pictures and in the Birnbaum world - everything is wonderful (I don't like a lot of the guides for newbies because you may find something wonderful that the UoG or Passporter isn't fond of). If they crave more after that - Passporter or UoG.
I'd give them a top ten pieces of advice list - just ten. Mine would be something like:
1. Arrive at the parks about fifteen minutes before they open. Getting up early in the morning at Disney will save you hours in line later.
2. With little kids along - head straight back to Fantasyland and ride Dumbo, then Peter Pan, then Pooh. You've just saved yourself three hours of lines.
3. Book a character meal, and book it in advance.
4. Don't try and see EVERYTHING. You'll hurt yourself.
5. Research before you go so you know what your family wants to see in each park.
6. With little kids, never start on dark, scary or loud rides. Work your way up.
7. If you want sit down meals, its best to make reservations before you leave home. But it isn't necessary to have sit down meals. Disney has good counter service, although again, it isn't bad to do a little research before you leave home so you don't eat burgers and chicken fingers for a week.
8. Avoid the shops (or at least buying anything) until your last day.
9. When you get tired, go back to the resort and rest or swim.
10. Figure out where you are. Understand transportation, the layout of the parks and how big Disney is.