I always find that i cock my wrist upward with the edge of the cards pointing towards the eyes of the spectator. This is just a natural position for me
I've found that when doing a riffle force you should let them see the side and the top of the deck at the same time.. But i really wouldn't let them see the indexes of the cards as i riffle the deck.. Make sure that they can see where you are riffling though.. and cover everything with your hand.. Luke Jermay has some really great subtilties in his riffle force.. I believe that it is in his easy collectors video (from penguinmagic.com) he shows some of them.. still it probably isn't worth the money unless you are gonna use the actually routine..
As a sidenote, when they call stop try and dig your fingers into the hole, then slide them out when you do the move. It's easier and looks more natural.