Usually when we're setting up the kingdom, I take the supply cards box, which contains everything except the kingdom cards, and my opponent(s) split up the three boxes full of kingdom cards. With two opponents, they can power through the kingdom cards by the time I'm done putting out the supply piles. With one opponent, he usually takes two kingdom card boxes and I do the third and he ends up waiting on me a bit. I keep the starting decks separated in the supply cards box. Yes, I realize that this means in 2/3 player games I'm not playing with enough copper in the supply, and yes, I realize I could remedy this by taking some extra treasure cards from Intrigue and adding them to the supply; but no, I do not care enough to do this.
Between games, I rarely touch the supply cards box, but if it needs touching I'm always the one to do it. It's very easy to miss that we need VP tokens or Trade Route tokens this game but I'm decent at catching those kind of things. The only danger of messing things up is when my opponent gets 12 kingdom victory cards out in a 2-player game (or puts cards away facing the wrong direction! AAH!)
I have an app that decides the kingdom for me, it's Dominion Shuffle by Joran Jessurun (for Android). I guess it's still getting updates, even though I thought it wasn't. I tried to get an Android App development environment set up on my home computer so I could either tweak that app or write my own, but that didn't work out and their tutorials/forums aren't competent/motivated enough to help me fix whatever is wrong. I'd like the app to put a little reminder at the bottom that VP Tokens will be used, Potions will be used, Curses will be used, etc. I'd also like for it to support veto mode, but alas...
Yeah I only get the curses out when they're needed. Less clutter helps me sleep at night. I know it's wrong, but you know what I always say: "If it feels good, do it." I get them out when Ambassador, Fairgrounds, and Watchtower are present (individually). I've never heard of someone buying a curse to help their Menageries draw, but if I see one log where it works, I'ma totally start doing it. Also, when someone is taking a long time to think about what they're going to buy, it's always fun to say "I can get the curses out if you want"