I'm currently ranked 39 with Zoo, so I'll give out what advice I can:
-Turn 1 is often the most important one, but how you mulligan depends on whether you're going first or second. When going first, 2-drops are a little more valuable since Young Priestess and Voidwalker are a little weaker on their own. When going second, the coin allows you to be really aggressive with your mulligan, as you'll often be able to play two 1-drops, and the coin is a bit of a safety net if you get a bad hand.
-Against miracle Rogue (or just Rogue in general, I guess) I've learned to devalue 2-health minions (i.e. Knife Juggler and Dire Wolf Alpha. Flame Imp doesn't change much because it's a 1-drop). Rogue has many ways to deal two damage, whether it's Backstab or SI:7 Agent or a desperation Eviscerate. Thus, I find Amani Berserker to be a little better in this matchup (they could do two damage+dagger, but that's a forced 2 mana and 2 or 5 damage to the face). The flip side is that Rogue has a few 3-health minions (SI:7 and Earthen Ring), but with the various ways to buff minions that's not a big problem. The most important part about facing Miracle Rogue is keeping up pressure. If you can prevent Gadgetzan from getting on the board you win (usually).
-I feel like Warrior is one of the easier classes to play against. The only way they can prevent you from getting board control is with Fiery War Axe, Cleave, and Cruel Taskmaster. Try not to have only two minions with 1 or 2 health, be weary of leaving your minions at 1 health, and just try to lessen the value of Fiery War Axe. Obviously Brawl is a card you have to keep in mind, so try to keep a good sized hand turn 5+.
-Druid removal consists of Wrath and Keeper in the early game mostly. Swipe and Starfall are your greatest enemies, so play around those as much as possible. Occasionally you'll be good for most of the game, and an Ancient of War pops up and you simply can't win. It happens.
-Against Hunter it's usually somewhat of a race. The big UTH turns don't happen until turn 5, so you can feel free to flood the board before then. Really, there isn't much to the matchup other than hoping your opponent didn't draw UTH. There's nothing a Hunter can do other than Explosive trap, and if you're careful that won't matter much. I don't run into many Hunters so I don't really have a feel for the nuances of the matchup.
Edit: I forgot to mention this: minion placement is extremely important. Always keep in mind where it would be best to place Defender of Argus or Dire Wolf Alpha. Generally, you'll want to keep more fragile minions in the middle so you can get extra DWA buffs, but you'll also want to keep passive minions on the outside like Knife Juggler and Young Priestess since you'll be less likely to trade them.
Edited by PresidentSDR on 6/17/2014 1:37 AM PDT