Shaman-tank
Shaman-tank or sometimes referred to as "Warden" is the playstyle of adopting the traits of the tank role in Classic Era and Burning Crusade Classic as a Shaman. In Season of Discovery, the tanking shaman role was officially supported by Blizzard through the addition of various runes.
The shaman class was not designed to fulfill the tank role during its original inception, but over the years, the shaman tanking playstyle improved through research and effort from the community to legitimize their role as an unofficial tank. Shaman, although, not the most optimal class to be played as a tank is still deemed to be a viable option. Shaman tanking is usually considered a sizeable undertaking that demands more effort than traditional tanking classes.
Shamans can fully tank 5mans, 10mans, off-tank & main-tank raids, though are reliant on personal and guild experience and support. Their overall defensive statistics won't reach a warrior's — However, it isn't necessary to do so in order to tank.
In Season of Discovery
Season of Discovery enabled the long-awaited shaman-tank into further playability through various runes that granted them new abilities:
[Decoy Totem]
[Shield Mastery]
[Molten Blast]
[Maelstrom Weapon]
[Way of Earth]
[Spirit of the Alpha]
These various abilities enhance their AoE and defensive potential, vital tasks that tanks take up in order to keep aggro from mobs.
Building a shaman tank
Once reaching level 60 in World of Warcraft: Classic, there are various strategies most commonly used by shaman tanks.
Suggested races
The Shaman class is exclusive to the Horde faction under the following races: Tauren, Orc and Troll. Future tank players intent on optimizing their character may opt to create a Troll for their racial, 
[Berserking].
Professions
When it comes to a shaman tanking, the most suitable profession is Engineering because of its numerous tools to aid in mob control and AoE, like the 
[Masterwork Target Dummy] and the 
[Goblin Sapper Charge].
Blacksmithing helps in obtaining 
[Sulfuras, Hand of Ragnaros], a powerful weapon in the shaman-tank's arsenal. If a player has access to the Ahn'Qiraj raid and the loot it has to offer i.e. 
[Dark Edge of Insanity], the Blacksmithing profession can be disregarded and the player can go a high gold generating profession on instead. Gold helps buy potions among other useful items for tanking.
Threat management
A Shaman can increase threat in many ways, notably: 
[Earth Shock], 
[Stormstrike], 
[Rockbiter Weapon] and 
[Lightning Shield]. Threat can also originate from items that replenish Health and Mana, ex: 
[Major Rejuvenation Potion] based on half of the Health & Mana gained. Items, which inflict damage, ex: [Goblin Sapper Charge] deal threat equal to the damage done so do reflective buffs, ex: 
[Thorns]. Lastly, certain items deal threat each time their Debuff is triggered, ex: 
[Gift of Arthas].
Allies may considering aiding the tank by reducing their threat, through mechanisms like: 
[Fetish of the Sand Reaver]. The Mage class can reduce their threat through the talent: 
[Burning Soul]. Shaman: Tranquil Air Totem. Rogues and Hunters wipe threat with 
[Vanish] and 
[Feign Death] and so can Flask of Petrification. Items prevent aggro: 
[Limited Invulnerability Potion] and redirect aggro: Masterwork Target Dummy. Classes in the 30-40 yard range won't get aggro until they surpass the threat level of the mob's target by 30%, as opposed to 10% for melee.
Totems
Shamans get access to a multitude of class unique totems, some totems can help with tanking, notably 
[Grace of Air Totem], 
[Stoneskin Totem] and 
[Healing Stream Totem]. Totems are incapable of generating threat for the Shaman.
Recommended talents
Shamans can go down three talent trees. The most relevant talent path for tanking being Enhancement, which delivers Toughness, Anticipation, and [Stormstrike] among other talents. The most popular talent point allocation being (16/35/0).
Recommended rotation
A certain rotation is advised to master your tanking potential. A tank rotation is split into three phases: Pre-pull, Pulling, and Combat.
- Pre-Pull
Before engaging the mob in front of you, cast Lightning Shield and cast Rockbiter Weapon. Place down Stoneskin Totem, Grace of Air Totem & Healing Stream Totem. Mark the mobs in front of you with a target marker, and using markers to designate the kill order and your group's use of CC.
- Pulling
Cast rank 10 
[Lightning Bolt], followed by as many rank 1 [Lightning Bolt] possible to trigger, 
[Elemental Focus]. Lastly, [Earth Shock].
- Combat
When it comes to tanking raids, it's adipose to use 
[Nat Pagle's Broken Reel] to assure the first few Earth Shocks hit. In a fight, use relevant ranks of Earth Shock that suits your mana & threat. Stormstrike can't be downranked but is also used in similar cases. If [Lightning Shield] expires, cast it. If you suddenly might die, equip a defensive weapon, ex: 
[Spineshatter] enhanced with Enchant Weapon - Agility & Rockbiter Weapon, use Masterwork Target Dummy, which will Aggro the mob, use 
[Juju Escape], possibly Major Rejuvenation Potion and 
[Major Healthstone].
Buffs and debuffs
There's a maximum of 32 Buffs, avoid nearing the max as it may result in Buffs getting pushed off, it's advised to install an addon to keep track of buffs. Prioritize getting defensive Buffs, ex: [Elixir of Fortitude]] before getting buffs that bolster threat, ex: 
[Juju Might].
A max of 16 Debuffs can be on a mob. Reaching the max is major in raids. There's defensive debuffs: 
[Insect Swarm] and threat Debuffs: 
[Faerie Fire] among others. If in a raid, ask the raid leader, if certain Debuffs can be placed on the mob, without overstepping.
Recommended attributes
Prioritize defensive stats when gearing, and threat generation secondly. It's advised to get 4k HP & 5k Armor unbuffed for Molten Core. Blackwing Lair, ~4800 to 5k HP and 6500-7k Armor. For reliable threat, 3% melee Hit is advised for dungeons. For Raid tanking, 6% Melee Hit. if survival seems grim mid combat, switching to a defensive weapon like [Spineshatter] is reccomended.
Tanking multiple mobs
Many actions can further solidify situations when a tank is dealing with many mobs, ex: 
[Oil of Immolation], Thorns, 
[Force Reactive Disk], etc. It's crucial to switch and attack another target ever so often. In combat, items & spells giving health or mana deal 50% threat divided by each mob. Items can also take help until a decent amount of threat is gained on all mobs, ex: [Masterwork Target Dummy].
Recommended raid composition
With the raid leader's consent, offer an ideal raid comp without overstepping.
Previous compositions that have worked include a warlock for 
[Blood Pact], a Warrior for 
[Battle Shout], a druid for 
[Leader of the Pack] a hunter for 
[Trueshot Aura]. Groups with high-threat damage dealers can have their shaman use Tranquil Air Totem.