If you know a fight will last four minutes or more, using Mana Tide Totem early will let you use it again a second time. It is generally a good idea to use the totem when you are around 70% mana, rather than waiting.
The short cooldown means you can use Mana Tide on trash pulls to reduce the need for drinking, and still have it ready again before the next boss fight.
When using Mana Tide Totem in a raid, try to ensure that the other healers will be in range of it as its range is a mere 10 yards.
Trivia
Although this is a "Wavestorm Totem" in the TCG, the artwork is used to represent a Mana Tide Totem in Hearthstone.
Mana Tide Totem appears as a rare card for the Shaman class in Hearthstone. The flavor text reads: "It is said that some shaman can say "Floatin' totem" 10 times, fast."
Mana Tide Totem has had its functionality changed several times throughout the course of the game. In the original World of Warcraft, it had three ranks, returning at a fixed amount of mana at each rank. In The Burning Crusade, it was redesigned to restore a percentage of maximum mana and consolidated into a single rank. In Cataclysm, it was changed to increase spirit, meaning that non-healers would no longer gain any mana from the totem. This meant that in a normal five man group, the casting shaman will be the only one to benefit. In raids, however, the totem will restore mana to every healer, rather than just those in the shaman's group.
Patch changes
Patch 9.0.1(2020-10-13): Reintroduced and redesigned.
Patch 6.0.2(2014-10-14): Removed. Restoration shaman Mana costs have been adjusted to compensate.
Patch 5.0.4(2012-08-28): Duration increased to 16 sec, up from 12 sec.
Patch 4.2.0(2011-06-28): Mana Tide Totem now grants 200% of the caster's Spirit, down from 400%.
Patch 4.0.6(2011-02-08): Redesigned. The totem no longer multiplies the Spirit of those affected by it. It instead gives a flat amount of Spirit equal to 400% of the casting shaman's Spirit, exclusive of short-term Spirit buffs affecting the shaman when the totem is dropped. In addition, its effects are now raid-wide.
Patch 4.0.1(2010-10-12): Radius increased from 30 to 40 yd. Changed from restoring 6% of total mana to every target each 3 sec to increasing Spirit by 350%. Cooldown reduced to 3 minutes.
Patch 3.2.0(2009-08-04): Totem health now equal to 10% of the shaman's health, up from a flat 5 health.
Patch 3.1.0(2009-04-14): This spell no longer costs mana.
Patch 2.1.0(2007-05-22): This totem will no longer sometimes grant mana after it has been destroyed. It will also consistently grant mana 4 times instead of sometimes 3 and sometimes 5.
Patch 2.0.1(2006-12-05): Mana Tide Totem now restores 6% mana per 3 sec, rather than a flat amount of mana per 3 sec. Additional ranks have been removed.
Patch 9.0.1 (2020-10-13): Reintroduced and redesigned. 
Patch 6.0.2 (2014-10-14): Removed. Restoration shaman Mana costs have been adjusted to compensate. 
