Media, or sometimes mediums, are old ladies wearing do rags that predict your future. The ladies do, not the do rags.
You may encounter a palm reader, who can tell what you had for lunch since you never wash your hands. This is what is meant by being a "sensitive". They can also tell your age by reading the dirt in the lines of your hand. When consulting such a medium, always remember to bring along your hands and not one you just found along the side of the road.
Some may use a crystal ball to tell your future. This is different from the palantir used in Lord of the Rings before the days of Skype. A crystal ball takes special powers to summon spirits or recipes, so you will see nothing from your side of the table it is on. Therefore, you should take some time to examine the crystal ball and the room. If you see 3 holes drilled in the ball and a bowling bag somewhere in the room, it is a bad sign. Of what, we do not know.
Other use tarot cards, cards with exotic and weird designs. Therefore, you are cautioned not to play poker or even Go Fish with any medium, as they often have the good Magic:The Gathering or rare Pokémon cards to beat you every time.
Some mediums talk directly to spirits of the dead. If you see any medium use a walkie talkie, they are probably not legitimate, especially if you can hear their spirit guide "Cochise" burping and farting outside the tent. Further, the use of 10-code ("Breaker, breaker! What's your 10-20, Cleopatra?") should also be a strong warning that perhaps your medium may not be genuine.