Don't choose the cards. You already have an advantage by knowing the game. Picking the cards and you're already picking favorites and thinking strategy before anyone else. Go random and go in blindly with them.
I can't agree with that just because some cards are not that newbie-friendly. I only need to point to Dark Ages for illustration.
Also, some cards can turn off newbies. Witches and Mountebanks, for example.
Besides, if you're a skilled Dominion player, then you're going to know all the cards anyway and can whip up a good strategy that'll trounce the newbies. A random configuration won't be a handicap for you, and you run the risk of souring the game for someone else.
To avoid that I take all the randomizers and look one card at a time. And I see if it fits on the board, if it's too complicated etc... When I have a card like mountebank in hand "hey look at that, believe me you don't want to try it now"
It permit to have a game somehow random but with no hard cards. And I remember a game where we had Harvest, Lighthouse and Bank: not too complicated and you can explain what are the expansions themes.
My priorities for the first game are :
- easy to play/understand cards
- some expansions variety
- no powerhouse combo "oh what a shame you didn't see the KC/Wharf/Goons combo, sorry for you"
- no obvious alternate way to game than province buys. And I explain dominion is so rich, that's not the best way to win on every game
- at least one attack but no curser (except jester), no pirate ship and no ghost ship
And I only explain a little strategy things:
- the too many terminal thing if an opponent goes that way
- if he wants to buy the first province I tell him "it can be a good idea to fasten the tempo of the game, but are you sure you want to do that ? you are the best to know if you have 8$ by luck or if you deck is able to do that regularly".
I always try to play optimal, I don't want my opponent to think Dominion has no learning curve, and I remember my first games when I saw my opponent draw his deck and I was like "I need to be able to do that one day"
For the moment nearly everyone called my one week after "hey I bought the base game, (what's the point of chancellor ?)". I think that prooves it's a good way to learn.