Mulligans
General Mulligans
Ideally in an aggro matchup, you want to mulligan for your cheap clear and a single Sea Giant. Mana Tide is also acceptable if you have Lightning Bolt and an AoE clear. If you begin with Thunderhead, try to dig for any 1 cost or lower overload spells.
In a control matchup, you will want to mulligan for Doomsayer and any card draw. Crushing Hand is also a great option. You often do not want to keep minions other than Doomsayer in this situation, but this can always change depending on your opponent's class.
If unlucky, card draw is always a safe option. Far Sight is your best friend.
This Giant deck is quite simple… use cheap clears to construct and destruct the board, whilst hand hoarding. This allows for the use of every Giant in standard, while using spells and Thunderhead to clear aggro. Essentially, this is a hybrid Big Shaman.
Utilize overload clear whenever needed in order to upgrade the spellstone and reduce Snowfury cost.
Try your best to protect Mana Tide, for it is a great boon towards your Sea and Mountain Giant value.
I often find that Ancestral + Doomsayer is an incredible stall in itself, buying you multiple turns or an extra 14 health.
This deck is best against aggro matchup, but does not falter against big minions. Ancestral Healing is not required, but adds more threat and recovery to your board (as well as Bog combos). Spirit Echo is a great addition for lategame, creating much more Hagatha value. Big spell decks are your weakness.