This is a support guide for Taric, the Gem Knight.
Playing Taric is an attitude, which consists of three states of mind:

Your job is, and always will be, keeping everyone safe and alive.

Granting Vision (and Denying Vision)

Buying wards until you get the sightstone so your ADC can farm safely and having vision of all the ganking pathways to your lane is the key task of the support. Also using your trinkets and pink wards to deny vision of the jungle paths and bushes is essential for succesful ganks. Placing wards or trinkets near their tower (not spottable) is also a viable option if your top champion has teleport.

Healing/Shielding

Taric's heal is one of the best in Runaterra because it scales with his own HP and doesn't depend on AP, this effect benefits from most of Taric's items, even the Sightstone.
Items such as Face of the Mountain, Mikael's Crucible and Locket of the Iron Solari grant further protection to your teammates.

Granting Auras

Taric, by his presence alone grants teammates with armor with his shatter and AD+AP with his ult, Radiance. Getting items like Aegis of the Legion, Zeke's Herald and Commander Boots will buff your entire team during a team fight, turning the tides of battle.

This will make sure no one ever ignores Taric in the battlefield.

Blocking Incoming Attacks/Abilities

You are a protective bulwark, you can take all the damage you can and still heal insane amounts of health, while granting buffs to your ADC. So don't be scared of being front line, because if they focus you, they'll end up receiving a lot more damage from your teammates.

Providing Crowd Control/Debuffs

While Taric's stun is perfect for picking up overextended opponents, he can always use shatter to significantly reduce your opponen'ts team Armor. Another side of this is buying items like Frozen Heart or Abyssal Scepter to debuff your opponents and make your team's attacks and abilities more powerful.