Dominion, as a deck-building card game, may seem to be all about adding good cards to your deck. However, an important thing to remember is that another way to improve the average card in your deck is to trash the bad cards. Here are some beginner strategy tips on how to thin your deck.
Why Deck Thinning?
In a game that's all about buying more and more cards to add to your deck, it may seem counter-intuitive to destroy your own cards. But the important thing to keep in mind is that you are trying to improve the average draw in your deck. And whenever you want to improve an average, you can either add things at the high end, or remove them at the low end. Ideally, you do both.
Your starting deck consists of seven Copper and three Estates. Almost every card on the board, including the Silver that is always available for purchase and affordable in your first two turns, is better than your Copper and Estates. Once you start buying cards, your new cards are trying to push your average card value up, while your Coppers and Estates hang around and pull that average value down.
To look at it another way, imagine that you bought two Silver on your first two turns. Your deck is now 2/12 Silver, so you have a 1/6 chance of any card you draw being Silver, and slightly less than 50% odds that any given 5-card hand will have a silver. But let's say you manage to thin your deck and trash six of your starting cards. Now your deck is 2/6 Silver, so you have a 1/3 chance of any card being Silver, and a guarantee that your 5-card hand has a least one Silver, with a good chance of both.
In short, trashing your bad cards puts your good cards into your hand more often. So now that you understand the advantage of trashing cards, what cards in the base set allow you to trash things?
Chapel is, bar-none, the most powerful deck-thinning card in the game. Chapel lets you trash up to four cards in a single action, and as such, is the perfect card for any serious deck-thinning strategy.
Chapel users should remember to buy Silver, lest you find yourself with not enough buying power once you've trashed all of your Copper. But if you want to get rid of your starting cards fast, Chapel is the best way to do it. The other cards will only let you trash things one at a time.
Moneylender trashes a single Copper, and gives you $3. In effect, this gives you as much buying power as a Silver would have, but lets you get rid of a Copper from your deck at the same time. This helps you improve your average card value in two ways at once, by removing a lowly Copper from your Deck, and serving as a boost to your buying power to acquire a new powerful card.
As with the Chapel, if you are lending all the Copper out of your deck, it is important to remember to buy some Silver (or Gold, if you can afford it) so your deck maintains buying power.
Remodel allows you to trash any card, and then gain a card worth up to $2 more than the card you trashed. This can be as simple as turning a Copper into a Cellar, or as big as turning a Gold into a Province.
The versatility of Remodel makes it a card worth playing the whole game through, from the early game to the late game. You can use it in the early game to get rid of your starting cards, and Estates can be turned into more Remodels. This strips your deck of a hand-clogging green card, and gives you even more Remodels to improve other cards faster.
Mine is unique in that while it technically trashes a card, what it really does is improve it. The Copper (or Silver) you trash from your hand is immediately replaced with any treasure costing up to $3 more, which in the base set means a Silver (or Gold) that goes right back into your hand.
In effect, the Mine accomplishes three things: It trashes a worthless Copper, it gains you a Silver, and it improves your buying power by $1. Later in the game, mining Silver into Gold is even more valuable.