Many beginners to the game come to the realization that the lantern forms a shield for themselves and teammates. While this is certainly a plus, it definitely does more than that. The lantern, when thrown correctly, has the best/fastest gank potential of any support. As long as thresh stays in range (large circle showing), a teammate can grab the lantern and swing to you. This can swing a 2v2 under your own turret to a 3v2 chasing the opponents down the lane.

As fantastic of a feeling as it is to set the hook, beginners think that they must swing on down to their opponent everytime. There is always a time and place for that. The hook, when landed, holds onto the opponent for around 3 pulls or 2 seconds. This gives the adc time to get some free shots down. If the time comes when your enemy support or adc is low on health and you hook them, wait until the three pulls are down then swing into the enemy. This will hold them for the longest time possible, allow to get an auto attack off, and a nice flay will kick them back and do damage.

Flaying an enemy can be down to push back an enemy or pull them towards you. Say a huge 3000lb volibear is chasing your adc and you need some time to save her. the flay will knock it back and hopefully save the carry. If you want to flay an enemy back, flip your mouse/flay behind thresh. He will turn around and flip the enemy backwards allowing for more damage