I've given tips to many, many Disney newbies. I've found that most of them are easily overwhelmed. So, I keep my tips to a minimum.
My first tip is always to get there early, take a break in the afternoon and go back in the evening.
Beyond that, I try to get a sense of what they are looking to do and then base my suggestions on that. If they are willing, I will put together a short guide-book they can follow. But not everyone wants that level of info.
Some people I've helped on previous trips will come back to me for tips on things they can do that will be new to them. I really enjoy helping these people, because I often get to research things I have not done myself.