it just depends.
You have to be that good of a performer, that when stuff like that happens, you can have the audience management to handle it.
It may mean make a smart comment or totally ignore them <--but make it a joke
never offend the spectator. Let the magic speak for itself at times.
And this stuff will always happen. There are always hecklers, so don't sweat it too much, just keep performing, and you'll learn how to react to the situation each time.
Maybe practice a way to get out of the heat if you can. Maybe change tricks right in the middle of the first trick. maybe for a Dl, turn it back over and since its now the second card, palm it over to your hand while they make their comment/ you look at them and their eyes meet yours.
Then say "ok, then, you shuffle the deck, it's all yours" <-- make the trick theirs now, giving the deck to the audeicne is always a good kicker.
And since you have the card in your hand, put it in any pocket and have them look through the deck for their card.
Something simple like that, to get out of the heat.
