re: Poker & Four of a kind are better on river or turn?
You also need to add something to your evaluation. You need to see how you reach quads. Do you have two in your hand, or three on the board. Two in the hand is worth WAY WAY more and should be played differently than 3 on the board.
Also, any time you can add a bet, or allow someone to think they have caught up (but obviously didn't) is better for you in the long run, so hitting it on the turn is better. HITTING ON FLOP IS BEST! - two extra bets and chances for a false catch up.
Quads are hard to slow play for value on most boards, because at least 2 must be on the board so people are already suspect of at least a boat being slow played. Unless there are 3 to a straight or flush by the turn its hard to get any value and people will not bet their top pair or even their over pair here in most situations, so best to bet a bit and hope for a call or a raise (of course there are cases where your opponent has AA KK or QQ in their hand and you should be aware of this by their betting pre and post flop - if you suspect this then definitely continue to slow play because they will bet again not thinking you caught anything - works best when only 2 of the quads are boarded)