You will have three cards, which appear to be this, this, and that. You show them in order, this, this, and that. Then you flip them all over. Then you pick them up (still facing down) explaining that that is on the top, so you put it on the bottom. But when you the pile over, it's this. So you flip the top card and it's also this. Then the middle card is this too. You explain you don't know where the that card is, and then flip the top card again and that is there. Then you flip the middle and that is there. So you show the cards all again. This, this, and that. But without changing anything, you show them again and they read this, that, and a card marked other.The secret is, you have this, that, and other the whole time, but you show this twice many times.There's more in between, and here's a good video on youtube of it even though I didn't make it, it explains it well.
https://www.youtube.com/watch?v=wD2IWM-g9vY