Ignite or Exhaust
I take exhaust for the 40% damage reduction, so i know my ADC is safe when i play against an assassin or any kind of high burst champion. It also offers 30% reduction to attack speed and movement, this alone is already enough reason why you should get exhaust. This is extremely crucial especially when you are laning with an extremely weak early-gamer like Vayne.
However, I do think ignite is good for ADC’s which are very strong early. A good example would be Draven. Getting ignite would put you in a disadvantage if your enemy team is constantly communicating with their jungler. Exhaust is an extra peel, never forget. I almost never get ignite except if I?m trolling in normal games. However, if ignite works for you go ahead and kill those bastards.
Many high elo Thresh players take ignite in Solo Q games and replace it with exhaust in Ranked Team games, reason why is because kills are crucial in Solo Q games. For ranked teams where teams are coordinated just don?t risk it.
Try it yourself and figure out which playstyle works for you.
These are very subjective. Thresh doesn?t really have a specific rune setup you should follow. Just be tanky and get a bit of AD. Again, you can decide on your own. I suggest some of these pages though, these are taken from Pros who actually ?know? how to play Thresh.
Madlife’s Rune Page
This is my own preference with my ability order, don?t go hostile on me for picking this because these actually work for me. Do whatever feels best for you.
Q: Death sentence: Death Sentence is like your power up in level 2. However, this does not mean that you should go aggressive and start attacking champs right away. Let them walk beside minions, make sure the enemy support isn?t close to follow up and try and land a hook. Of course there isn?t a guarantee you will hit the enemy ADC, but if you do, that?s automatic a few seconds of free auto attacks for your ADC.
When practicing with your Q, try hitting them at close range, and slowly try ?longer range pulls. Don’t over use your hook. Every time you miss you look ridiculous and look like you can’t play. It also costs lot of mana early on, so I recommend being rather reserve your Q. The cooldown is reduced a few seconds if you hit a target, so keep that in mind. Double press Q on a target to pull yourself to them. This is not really recommended unless you have backup around you, and it?s a 2v1.