Last new player I had I told only two things: roll 8+ to succeed and don't annoy anyone in BattleDress with an FGMP.
Yea, so much this.
Someone was trying to get us back in to a D20 game, Pathfinder I guess it was. And he wanted us to go through all these books and what not.
I basically told him "If I'm not killing monsters within 15 minutes of sitting down, then I'm not coming".
Maybe a skilled player wants to know the rules, but early on the GM should just be guiding us through the mechanics and the story. It's an RPG, not Squad Leader.
"I listen at the door what do I hear?" "Roll some dice" "7" "You don't hear anything." See, I didn't really need to know the "listen" mechanic, task, skill, or whatever to do that. HE did, the Ref, but I didn't.
Ref presents situation, players react. Ideally Ref doesn't put beginning players in to situation where understanding the nuances of moving grazing fire while crouched in a smoke filled room with limited visibility but an infra-red sight will make any difference. "Ah, see, the scope gives you a 17% better chance at success, but encumbers you, limiting your actions on High-G worlds." "Umm..did I hit the guy or not?" "No." "Ok, I fire again." "You might want to take a turn to aim, since dancing will affect your chances at hitting." "Oh, ok. I stop dancing. Then I'll fire." "That will be next turn." "Ok."
Heck in many ways, it's better for the players to not know the rules, then you have fewer rule lawyering arguments.
"But the book says..." "Yea, and it also say I can do whatever I want cuz I'm the Ref" "Well why have rules at all?" "That's stupid" "You just hate that my elf got her ears bobbed." "Say, can I have some chips?"