Smite is generally used for jungling. Beyond dramatically speeding up clear time, its high damage provides a strategic last-hit advantage at high-priority buffs like Dragon and Baron Nashor.
Smite can also be used to push a lane more quickly. When doing so, it's generally best to save Smite for siege minions.
An unconventional use of Smite is to instantly and unexpectedly kill a minion to land skillshots such as Rocket Grab or Death Sentence on enemy champions behind it.
Smite deals true damage, so it will always deal the stated amount; it cannot be reduced or amplified in any way other than a few exceptions, such as the bonus damage against the Rift Scuttler under hard crowd control.
Can now be upgraded through the purchase of any of four different jungle items
Cooldown increased to 60 seconds from 40.
Smite Rewards added:
Smiting the Ancient Krug grants Gift of Heavy Hands - stuns minions and monsters every 1st and 5th hit. Your first attack against a turret deals 50 (+15 per level) true damage but consumes this buff. Lasts 90 seconds.
Smiting the Crimson Raptor grants Razor Sharp - gives you a warning and magical sight for 10 seconds when an enemy ward spots you. Lasts 90 seconds, with 1 charge.
Smiting the Greater Murk Wolf creates a Rift Spirit - summons a Rift Spirit that watches over a portion of the jungle. Lasts 90 seconds, but that timer goes down when the spirit chases enemies.
Smiting the Gromp grants Gift of the Toadstool - attackers are poisoned for 6 (+ 6 per level) magic damage over 3 seconds. Lasts 90 seconds.