Hearthpwn

Here's a guide and possible replacements:

You can keep 20 out of the 30 cards in your deck in your starting hand. Mulligan for almost any of the one to four cost cards:

One Avenge, one Noble Sacrifice, Redemption, Argent Squire, Annoy-o-Tron, Knife Juggler, Mad Scientist, Shielded Minibot, one Muster for Battle, one Consecration, Murloc Knight, and Piloted Shredder.

What not to keep is a smaller list. Do not keep Competitive Spirit, Repentance, Quartermaster, Mysterious Challenger, Dr. Boom or Ragnaros the Firelord.

Turn 1 Avenge, Redemption, or Argent Squire are ideal. Play a two cost minion if you have the coin.

Turn 2 All four two cost minions are good but Mad Scientist, Shielded Minibots and Annoy-o-Tron are particularly good. Save Knife Juggler for turn three unless you played Redemption turn one.

Turn 3 Knife Juggler, any of the other two cost minions and a secret, or your first Muster for Battle if you have two.

Turn 4 Muster for Battle. Sometimes you hold unto this guy and play more low cost minions or a four cost minion this turn to bait removal. Turn 5 then becomes Muster for Battle + hero power, turn 6 Quartermaster and so on down the list.

Turn 5 Quartermaster: Replaceable with Frostwolf Warlord. You'll most likely get away with buffing two silver hand knights and getting a cheap board clear (eliminate any taunts, big threats, or small minions you can pick off and minimize killing your minions that turn) or a swift six damage to face. If they all get killed, don't play him yet. It is guaranteed to buff one silver hand knight later.

Turn 6 Mysterious Challenger: Irreplaceable. He turns the tide by turn six every time. Play him and not only do you get a  board clear from the minions you buffed on turn five, you also get a pseudo free turn when the other player has one minion on the board. That minion attacking on their turn activates Noble Sacrifice, Avenge and Repentance. You'll most likely have a fat minion left on the board, a bunch of smaller minions buffed by Competitive Spirit, or both by turn seven! If by turn six, you have no minions on the board, it is usually better to hold unto Mysterious Challenger and play one of your Murloc Knights + hero power.

Turn 7 Dr. Boom: Irreplaceable. He is too perfect a minion to get a win by turn eight. If you did not play Mysterious Challenger on turn six, you can potentially play Dr. Boom turn seven, and then Mysterious Challenger on turn eight + hero power, potentially increasing the number of minions that get affected by Competitive Spirit.

Turn 8 Ragnaros: Replaceable. By turn eight in a typical match, you may need a final push to finish the game right then and there. Tirion is a great replacement and Kel'Thuzad is also a good replacement.