I've got 5 shammies, but 4 will arena and 5 will BG.

My initial drop is a castsequence for each on the same keybind.
Tremor pulses every 2 seconds, so I get two Tremors out spaced a second apart, as part of my initial sequence.
Four grounding totems are placed pretty much immediately as well.

Totem of Wrath, Wrath of Air, Mana Spring Totem, Stoneclaw Totem
Grounding Totem, Tremor Totem, Healing Stream Totem, Searing Totem
Tremor Totem, Grounding Totem, Healing Stream Totem, Searing Totem
Grounding Totem, Fire Resistance Totem, Frost Resistance, Earthbind Totem
Grounding Totem, Searing Totem, Healing Stream Totem, Stoneclaw Totem

All of the shammies have Grounding Totem on a hotkey, for immediate placement of five groundings at once.
Once my initial totems are down, I'll spam my Tremor Totem macro:

/castsequence reset=5 Tremor Totem,,,,
/castsequence reset=5 ,Tremor Totem,,, (etc)

Since the pulse of a Tremor totem is 2 seconds, I'd ideally like to press the key every 0.40 seconds in BG's (with 5 totems) or every 0.50 seconds in Arena (with 4 totems).
That way, Tremor pulses every half-second or so. They were part of the initial set, but this is much better protection from a fear-bomb.