Hearthpwn

Key combos / interactions

Combo1
t7: Earth Elemental+Ancestral Spirit
t8: (you have 5 mana after overload 3) Faceless Manipulator

Combo2
t9 (thaurissan proc): Earth Elemental+Ancestral Spirit+Faceless Manipulator

Combo3
t10: Kel'Thuzad+Reincarnate

Steal-your-stuff-combo
Faceless Manipulator +?Hex +?Ancestral Spirit +?Reincarnate

Huge-removal
t5: Elemental Destruction+Lava Shock

Combo1 is easy early setup, with high risk of removal. Should use this against aggro decks, but try to bait silence before you do it. If you put that on a board full of minions - don't expect it to survive (but you can expect it to clean the board). Faceless Manipulator isn't mandatory, but very good to have (sometimes opponent choose not to trade until they know they could kill it).

Combo2 is enough to finish off most games. It's total of 32hp, placed on taunts that hit for 7, means that if opponent tries to push it with minions - every minion die after a trade. It's very unlikely that opponent can deal with those (at least, not in one turn). Except for warrior, he can clean this with his best removals (Brawl Shield Slam Execute...)

Combo3 is here to deal with control-to-fatigue decks, that have shitloads of removals and can clean several combo2 setups. We can't win in fatigue, as we draw too much, thus we need just more huge setups, to ensure they lack removals for those. This is a backup plan, basically.

Steal-your-stuff-combo
This one is definitely fun, but somethimes not that effective (as you waste combo2/3 pieces). You can clone stuff with ancestral+reincarnate, but you are vulnerable to AoE after that. Still, it's beneficial to clone Archmage Antonidas, and hex his one, for example.

Cards

combo-section (explained above):

Kel'Thuzad - can be played on it's own, if something useful is on the board.
Reincarnate - combo piece, have little value outside of it. Can be used to heal up damaged minion, can be used to debuff enemy minion.
Earth Elemental - can be played on it's own in case of emergency. Can be followed up with Lava Shock.
Ancestral Spirit - key combo piece, have little value outside of it. This one is critical here, don't waste it.
Faceless Manipulator - can and should copy anything big survived next turn after combos.
Don't keep those in your starting hand.

card draw:

Mana Tide Totem - one of the best things over there. Heals your face for 3 (as it has 3 hp and must be removed), can draw more than one card. Keep one in your starting hand.
Coldlight Oracle - cuz we need those cards. If we give cards to aggro and draw AoE removal, it's still better than we don't draw AoE removal. And against control - it's downside isn't really a downside, cuz you can burn something. This thing don't put us on overload too, which is good. Keep if you expect no aggro.
Far Sight - cycle through the deck and put ramp into it, enables crazy combos unlisted above. Worst case scenario you pick 2-mana card, it wich case it's cycle for 1 mana. And most 2-mana cards is combo pieces anyway, so 0-mana cost is awesome there (0 mana Lava Shock is broken). Keep those in your starting hand.
Ancestral Knowledge - worst draw in the early game. Any other option can be used on t3, this one you should use much, much later. Prefferably on the same turn with Huge-removal. That's why it's x1 here. Never keep it in your starting hand.

survival section:

Mana Tide Totem - double it here, cuz it's "heal for 3".
Doomsayer - the best card early. You should mulligan for it. It's either heal for 7 for just 2 mana (and possibly waste burst on it), or it just kills everything on the board, or you bait silence/other hard removal. Every option is good.
Hex - best single-target removal ever. Should try to hold at least one in hand in case of emergency, and use other options if you can. Keep one in your starting hand.
Lightning Storm - this thing saves your life t3 (well, it does kill 2-hp stuff, and can kill 3-hp stuff with prayer to RNGsus), and doesn't completely screws you up if you don't Lava Shock afterwards (2 mana on t4 is enough to drop Doomsayer, for example). It also don't kill your own board. You should keep it if you expect aggro.
Elemental Destruction - should combo it with Lava Shock unless you NEED it. If you do, put Doomsayer on the board same turn, so you don't have to clear the board for the next turn, when you have no mana to do it properly. Shouldn't keep it unless have Lava Shock in starting hand too.
Refreshment Vendor - I love this card. It comes with Sen'jin Shieldmasta body, except it heals you for 4. So it's total hp gain is 9, not 5. Should keep only if have perfect mana curve already.
Vitality Totem - heals for at least 7 for just 2 mana. Can heal way more if you have some 7/8 taunts on the board. Shouldn't keep.
Lava Shock - best use is to combo it with overload cards, obviously. Can kill 2hp creature if absolutely necesary, can finish off creatures after AoE. Shouldn't keep it unless have Elemental Destruction in starting hand too.

Anything else? Ask in the comments.