How do you go about teaching the game in general to new players?
I uh explain the rules? "This is a game of building a deck..." I explain the data in the game - "you have a deck, a discard pile, a hand of cards..." I explain how your turn goes. I explain the card types, the four +'s, gain/trash, the end condition. I am teaching the game using whatever expansion I am testing, so I explain whatever twists it has.
How many games of Dominion would you guess you have played?
Man. Well, in the thousands. IRL I must have played at least 3K games; it's hard to estimate because any given game night may have involved other games. There are 3600+ posts in playtest forum threads for posting results from playing online; they aren't all games and I'm not in all of them, although a lot are and I'm in a lot of them. That doesn't cover all online games, just from Cornucopia on (I had a bad online version when working on the main set).
What card do you think you are "best" with? What about worst?
I'm best with new, untested cards. Also against them.
I'm looking at the sets, I don't see cards that say I will lose. I buy the weak cards less often than the strong cards, the narrow cards less often than the flexible ones. I guess like anyone decent can say, I do worse against swingy cards.
Boxers or briefs?
Boxers; the motif on them is a boxer, poised to punch.
Which is more frustrating for you in a competitive-ish game, Turn 5 chapel or 2+P in a Familiar game?
Well I've experienced the former more than the latter so I guess that one. But really, if this game is competitive-ish, phew, I can point to this as why I lost. The pressure's off.