The Black Market (promotional) card requires considerable set up time.
Before the game, make a Black Market deck out of one copy of each Kingdom card not in the supply.
There are a few ways to approach this:
1) Follow directions literally: take 1 of the 10 cards from each Kindom. For those with several expansions, this would involve drawing over 100 cards, and even more time consuming, putting away these cards when the game is over. Depending on the number of expansions, this could add anywhere between 3 and 15 minutes overhead per game.
2) When we first got the card we used it a lot. So to save time, we did not put away the extra card - instead we always kept a single card out for each Kingdom. This saves on put away, but when setting up the game you have to find the 10 cards for the game (whether or not Black Market is used), which adds 3-4 minutes to every game.
3) An idea we'll soon try: Use the randomizer cards for the Black Market deck, removing the 10 cards in play (which is especially easy if you randomized Kingdoms for a given game, as you already have the cards out). Then, each time a Kingdom is purchased from the Black Market, the regular card is pulled and placed into the purchaser's discard pile, while the randomizer card is removed from the play area (The back of Randomizer cards are a darker shade of blue so that's why you don't want them mixed in with the regular cards).
(1) is too tedious and we'll never do it. (2) was doable but still a bit of chore. I suspect (3) will be best though we haven't tried it yet.
On the other hand, perhaps Dominion players have come up with better methods?
Obviously this is not an issue with online or other form of electronic play, but I'd like to know about the best way to minimize Black Market set up and clean up time with regular play.