Advantage of memory in a Duel

One of the basic rules of Yu-Gi-Oh is you need your deck to at least Set some Spell and Trap cards. This is a prerequisite for them to be activated on your opponent's turn.


However, sometimes, you sometimes set more than one Spell/Trap card(s). What I was wondering about is: How do people handle their Face-down cards? Do they remember the cards when they Set it and activate them in responses to their opponents' moves quickly? Do they have to "peek" every time their opponents plays or activates a card? I am imagining that it is mandatory to memorize your Set cards in major tournaments or big events like the World Championships, but as for casual play, I think it helps memorizing and quickly activating your cards at the right moment.

I see some players peek on their Spell and Trap Card Zone every time their opponent plays a card. In my way of thinking, the disadvantage on this is that you will give away or at least drop a clue on what those face down card is/are. If they see you peek at your Traps while they play a Monster card, they can easily assume that it is a Bottomless Trap Hole. Thinking for too long after a Spell card is activated might let your opponent think that your Set card is a Dark Bribe or Solemn Judgment, with you taking your time to decide whether to let that card "go" or negate it.

It is helpful to set up a poker face while playing the card game as this might give your opponent the element of surprise and uncertainty. You could Set a random Spell Card and your opponent might think it as a Solemn Judgment, downing his aggressive play a bit(assuming he plays safely). Although the payback for this is that you run the risk of those Set up "decoys" being ruined by Card Effects though such as Gladiator Beast Bestiari or Heavy Storm.

So, how do you handle your Set cards?