Hearthpwn

No guide, but some tips:

Mulligan:

Generally you want to mulligan for a Fire Fly to kick things off. The best follow-up is Earthen Might T2 and 3-drop/firefly token+totem T3, so keep earthen might if you have the Fire Fly in your opening hand

Board control is King for this deck. You have great tools to win the board early on with Earthen Might, Flametongue Totem, Zap!, and Lightning Bolt, as well as swinging boards back in your favor with Fire Elemental, Blazecaller, Kalimos, Primal Lord and Lightning Storm or set up a swing turn with Glacial Shard. So use your resources wisely:)

You have a potential of 19 burst damage from hand for 10 mana with Leeroy Jenkins + Flametongue Totem + Windfury + Lightning Bolt, but don't hesitate to break up the combo if the situation requires it!

The 2 worst matchups are Cubelock/Controllock and Face Hunter:

Against SMOrc Hunter the only source of healing you have is Hagatha the Witch and Kalimos, Primal Lord, so if you don't have them in hand then try to race them by throwing everything at their face:) YOu can get there!

Against Warlocks going very aggressive early on is usually the right strategy (T1 Fire Fly, T2 Earthen Might, T3 Nightmare Amalgam creates a non-hellfireable board, that you can follow-up with Flametongue Totem and the Elemental chain:) but if your hand doesn't allow it then take it a bit slower: try to kill the Lackeys and Hex the demons right away to stop cube shenanigans and if you have Hagatha in hand try to stall untill you can get her online and hold back some minions to get more value. If you're running into lots of Warlocks and have trouble against them you can consider subbing a Nightmare Amalgam with an Acidic Swamp Ooze and/or Servant of Kalimos with a Spellbreaker.

Every feedback is very welcome!