There is a way to scam people on
three card monty without using a
ringer, using some farily simple
sleight of hand. I shall try and explain without diagrams.
Firstly, take 3 cards (typically a black queen, and 2 red cards).
It helps a little to bend these cards along their long axis such that when they are face down, they form a little tent shape.
Hold your left hand such that your palm is facing you.
Place the black queen in this hand, face up, it's long edge running in the same direction as your fingers.
Grip this card using the very base of your thumb, and the very base of your fingers. In fact, you can partially grip this card using the actual palm of your hand.
Place a red card face-up on top of this card, but this time, grip it using the tips of your fingers, and higher up on your thumb. What you want to achieve is a small gap (perhaps a quater of an inch) between these cards.
Hold the remaining red card in your right hand.
Show the cards to the audience and turn your hands palms-down, so that they cannot see the faces of the cards.
Now the tricky part. As quickly and as cleanly as you can:
Moving your left hand from left to right, throw/drop the black queen onto the table face down to land towards the right half of the table.
Moving your right hand from right to left, drop the red card face down to land towards the left half of the table.
Moving your left hand from left to right, throw/drop the remaining red card onto the table face down to land between the first two cards.
Now quickly (or slowly and deliberately if you're feeling showy) move these cards around (drop the right card over the middle card, drop the left card over the middle card, repeat) to try and lose anyone who may have followed you.
After the cards are first dropped, the order from left to right is RED-RED-BLACK, however, the audience will assume that you dropped the lower/easier/more obvious RED card first, since it is "on top", meaning that the audience thinks that the sequence is RED-BLACK-RED.
Take your bets. If you practice and are lucky, you should be able to win 4-5 times before anyone catches on. You can vary the initial positions of the cards and the throwing order if you like.
You can also feel less shame about taking their money, as you are using some sort of skill, as opposed to directly cheating them. Try it on your friends in a pub for beers and show them the trick afterwards if you like. You'll end up with a free drink or two, and they'll be less likely to be scammed in future and will be pleased to have learned something pretty cool.
And remember, PRACTICE this first.