Here's a trick you can try on your friends , it's pretty basic when you find out how easy it is you will be amazed at the simplicity of it.
All you need is just a plane deck of cards and a sharp thumb nail, we will get to the thumb nail in due time you can try this trick on anyone you feel the need to. Take your deck of cards and hold them up and spread them in your hands to who ever you are doing this trick to, ask them to pick a card from anywhere in the deck, it really does not matter where they choose to take the card from in the deck, so to make it sound a bit more realistic tell them they can take one from anywhere in the deck .
Now this is where the trick begins , have them look at their card make sure it is facing towards them so you cannot see it and say to them " take a good look at your card and don't tell me what it is" now not being too obvious take the card from them using your index finger and your thumb and then say to them once again in a louder tone " are you sure this is your card!" now at this stage you have the card between you index finger and your thumb right! now here's where it gets interesting, while holding the card between your index finger and thumb, press slightly on the corner of the card with your thumb nail this will leave a mark on the corner of the card. Now you can hand the card back to them with out looking at it, and say something like " alright then just as long as you know what it is" because now you certainly do! because it is now a marked card, so no matter where in the deck they put it you will easily find that card.
Just remember with this magic card trick to make sure you know which corner you marked and which side up the card is placed back in the deck, otherwise you could give it away looking at the cards from all angles while searching through the deck. Now with any true magic card trick the key is to practice and practice until it becomes second nature. Once you have done this it will look so much more realistic to your opponent and they will never suspect a thing.