In the magic the gathering there are winners and then there are cheats, if you suspect a cheat be sure they are actually cheating before accusing them of the fact that they are. Sometimes it can be a honest mistake which they are not aware of, they may have not played the game before and start making moves out of place. In this case you may have to go over the game with them before hand just to clarify the moves. so be sure. If it is a serious game and you are hell bent on winning no matter what the cost you maybe able to find someone to act as a judge to overlook any suspicious moves that may occur when playing the game. Get your father, mother, brother ..etc I think they would be more than obliging to help out. then the judge can quickly settle any disputes without offending your opponent , or stepping him outside for a tune up, but let's not go there. Only when you are absolutely convinced that your opponent is definitely a cheater then step him out..... na just kidding on that one but don't be shy to let as many other game players know about this person and their way of cheating , because if they are going to do it to you then they will do it to others as well.
The most common form of cheating is doing it in a way where it's deceptive and hard to see the deception your opponent has done In this case hold the game and tell the judge your concern. Something you should do is keep a vigilant eye on card counts, especially the cards in your opponents hand, and what cards they are landing. If you suspect their numbers are a bit shady then it's time to call in the judge once again, but be prepared to have a good reason why the totals are not correct. In this case you can use your own card count as a balance, just remember that your opponent may have used a card effect which would throw off the ratio, in any case the person who played first should always have one less card in total, in hand, in play, and in the graveyard.
There are many way to cheat at this game , but if you play with diligence and wit you will eventually out play your opponent with ease. Always have a keen eye on every move that is played, never ever let your cards out of you site. It can take a split second to swipe a card from your deck without you knowing. All said and done the magic gathering card game is a game that should be played with fairness, honesty and fun.