okay, i will share one with you...u will need a volunteer, a table and a deck of cards.
get a peek at the bottom card. spread out the cards face down on the table in a random heap, knowing where the bottom card is located in the random heap. the revelation is, that the volunteer will correctly choose 3 cards from the heap that the magician calls out. so, if the magician says 3 of hearts, 5 of diamonds and king of hearts, the three cards the volunteer choses are those exact cards when revealed.
since u (the magician) knows what the bottom card is, u say to the volunteer to choose that card u peeked at. of course, the volunteer can only guess where that card is. the volunteer points at a card (not the real one, more on this later), and u pick it up, and have a look. say it is the 4 of spades. place it face down, away from the pile, and then tell the volunteer to guess where the 4 of spades. do this same routine ie: look at card, tell volunteer to guess where card it, pick up volunteer's selected card.
now, when u call the volunteer to pick up the 3rd and final card, you say "let me help you", and u pick up the bottom card, cos you know where it is.
finally, reveal the 3 cards selected. they are the cards the volunteer has picked out at random, from the pile.
now, IF the volunteer happens to pick the bottom card FIRST UP, just say "well! what a relevation! good hands!", something like that. dont proceed onto the trick above, just move onto the next trick.