Play cards on curve so that you can outvalue your opponent in the early game which leads to a good board state for finishing off your opponent. The time to be pushing damage to face should be done in relation to the matchup and is something you get a feel for the more you play the deck. The headline here is to play minions on curve, make trades that give you a stronger board state than your opponent, combo cards together for stronger value(Houndmaster on a Ratpack or Crackling Razormaw to a minion that stuck for a turn), and PLAY AROUND AOE. Think about how bad it would be if your opponent had the means to cast one of their AOE spells/minions.
ALWAYS look for a one drop. Alleycat is the best card in your opening hand followed by Jeweled Macaw. The Alleycat into Scavenging Hyena combo is always welcome in your opening hand. If you have a 1 drop and a 2 drop its best to fill out the hand with any 3 drops. The goal is to have your early game set from the jump and draw into all of your bigger threats and play them on curve as well.
Warrior: It’s either against Quest or Pirate most likely. These are both very tough matchups if you draw bad. Against Pirate, you will likely be racing while making value trades and against Quest, you are often hoping for an early snowball to get rolling before they hit you with too many taunts or a good brawl.
Rogue: This deck does very well against quest rogue. Just start aggressive and stay that way. OTK control rogue is a bit tougher because of the sheer amount of removal contained in these decks. Look for small combos and don’t waste chances to push big damage to the face.
Mage: There are a lot of mage variants out there at the moment. The best thing you can do is play around their AOE and be aggressive. Some of the Mage decks out there, like Exodia mage or Freeze mage, play a bit slow so don’t miss chances to get them into lethal range.
Paladin: The goal is to kill the paladin before his late threat bombs start dropping. Deadly shot against Ragnaros or Tirion might allow you to push that last bit of damage through.
Priest: Don’t allow them to get much value off of Northshire Cleric. Using a Kill Command isn’t a bad idea if it prevents the priest from drawing cards. Dragon and Purify priest both have large minions that can control the board state. It’s best to keep minions off the board when you can.
Hunter: Have a better opening hand than them. It sounds like a no duh thing but most hunter decks out there right now are running the same 24 card base with some slight variations depending on the player’s tech choices. Make better trades and think about how you can put them in a position to get the least value from their combos. Watch out for overextending into Unleash the Hounds!
Warlock: Discard Zoo is likely the matchup and can be difficult if they get lucky on the discards. It’s hard to come back when they do things like Soulfire your Misha with a Melch’s Imp and the discard is a Silverware Golem. Just play the matchup normally and hope for the best.
Druid: Aggro or Quest are both played the same way. Out value your opponent and get a better board state.
Shaman: It’s likely elemental which can be interesting. Just play around their AOE the best you can and hope your momentum doesn’t get double hexed, which can be backbreaking.