Deckbuilding

There are many different ways to build a Midrange Hunter deck, but the core of the deck is always the same.

2x Haunted Creeper
2x King's Elekk
2x Mad Scientist
1-2x Eaglehorn Bow
2x Kill Command
2x Savannah Highmane
1x Dr. Boom

Aside from the core cards that make up the deck, there are a lot of optional cards to choose from, like these:
Hunter's Mark
Tracking
Explosive Trap
Snake Trap
Freezing Trap
Unleash the Hounds
Animal Companion
Steamwheedle Sniper
Houndmaster
Gahz'rilla
Zombie Chow
Acidic Swamp Ooze
Knife Juggler
Mind Control Tech
Kezan Mystic
Piloted Shredder
Bomb Lobber
Antique Healbot
Loatheb
Sludge Belcher
Sylvanas Windrunner
Webspinner
Quick Shot
Ironbeak Owl
Flare
Stranglethorn Tiger
Stampeding Kodo
Jungle Panther
Ram Wrangler
Dreadscale
Powershot
(Card #2982)

Playstyle

The Midrange Hunter playstyle is very similar to most midrange decks out there: make the most efficient plays possible. Keep in mind how much burst you have left, and start attacking face once you've drawn a Kill Command or double Quick Shot to start setting up lethal. Also, play it safe. Always assume the Mage has Fireball, and always assume the Hunter has Kill Command. If your opponent doesn't have lethal on board, use a Antique Healbot or Loatheb to prevent lethal from a burst damage spell. Always assume the worst, and you should do well.

Mulligans

Always keep solid early game like Quick Shot and Haunted Creeper. Against aggressive decks, cards like Explosive Trap and Unleash the Hounds are extremely valuable and should always be kept. Against midrange and control, standard mulligan rules apply. Against Warrior (one of this deck's worst matchups), mulligan your AoE damage and Knife Jugglers, because they are practically useless vs Patron.

Matchups

Ramp Druid: Hunter vs. Druid is mostly a toss up. Hunters control the early game and Druids control the late game, so the faster your draw, the better the matchup.

Face Hunter: Midrange Hunter has an excellent matchup against its baby brother. Both Unleash the Hounds and Explosive Trap tear face decks to shreds.

Mirror Match: Obviously this is a 50/50 matchup, but playing tech cards like Acidic Swamp Ooze and Kezan Mystic will swing the odds in your favor.

Mech Mage: Mech Mage has lots of efficient board control tactics and can burst you down early. However, taking out their mechs will help you out lots. AoE in addition to cards like Quick Shot will allow you to get strong, early board presence.

Tempo Mage: This is a great matchup for you. You can counter a lot of what Tempo Mages can throw your direction.

Freezemage: Unlike Tempo Mage, Freezemage is quite a bad matchup. Due to a lack of aggression on your part, the Mage can just throw up barriers until they can combo off and kill you. Your cards like Unleash the Hounds are duds, and you can't reliably deal enough damage in the early game to Kill Command your opponent down and break their Ice Blocks.

Shockadin: Just like the Face Hunter matchup, this should be an easy win.

Secrets Paladin: This matchup is generally a little bad for you, but Flare will throw this matchup heavily in your favor.

Midrange Paladin: Unlike Secrets Pally, this matchup is just about a 50/50. Whoever has the better draw generally wins the matchup.

Dragon Warrior: Lots of early game taunts can mess with you, and you are usually unfavored in the late game, so this matchup is bad.

Dragon Priest: See Dragon Warrior.

Control Warrior: Efficient early game removal and an excellent late game tips the scales in the favor of Control.

Face Shaman: See Face Hunter.

Midrange Shaman: Shamans can get you amazing value off of Unleash the Hounds, which pushes this matchup somewhat into your favor. Also, you tend to have better minions and a better curve than them.

Control Priest: Most of your cards die to Auchenai Soulpriest+ Circle of Healing, and on top of that, quite a few of your cards are almost useless against Priest, so this matchup is definitely suboptimal.

Fatigue Warrior: Fatigue Warrior is a pretty solid matchup. You can flood the board with sticky minions and Coldlight Oracle doesn't affect you.

Oil Rogue: Rogues have efficient removal, but it's hard for them to deal with sticky minions and lots of decent sized minions, something Hunters have in spades.

ZooLock: ZooLock's main goal is to try to outvalue you with early Mal'Ganises and strong minions, so you just need to outvalue them. If you make efficient trades and utilize your removal/silence correctly, you should do fine.

HandLock: If you draw the tools you need to efficiently remove big taunts and burst your opponent down quickly, this matchup should go well, but it's about a 50/50.