If the top card of your library changes while you're casting a spell, playing a land, or activating an ability, the new top card won't be revealed until you finish doing so.
15-04-2013
wotc
The top card of your library isn't in your hand, so you can't suspend it, cycle it, discard it, or activate any of its activated abilities.
15-04-2013
wotc
When playing with the top card of your library revealed, if an effect tells you to draw several cards, reveal each one before you draw it.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.