Lane: Bottom, Mid and Top (APC)

Why?

AP Thresh is OP Thresh.

And if you sneer at the though of an APC then just remember Thresh is the best carry because the longer the came goes on, the stronger he gets. Why? Because he can have a maximum of 999999 souls giving him 500,025 ability power and armour.

During the lane Thresh is easier to last hit with than most ADC because his auto-attack does more damage the longer it goes between uses. Say the his a minion that isn't quite one shot being focused by the creep, take the one next to it on half health and come back to it.

And never forget; Thresh is ranged.

Against Champions:
Q(Skill shot) then use your E to either push them away or drag them in close based on your instincts. Think you can take'em? Pull them closer. Think you can't? Push them away. Do not forget your lantern dropped at your feet can provide extra sustain and can also collect you souls.
Now if you are level 6 then pop your ultimate and then push them into your wall. Keep harassing them until you 'gank' or push them from lane.

I whole heartedly, though have not tried, recommend these support champions for Thresh. . . I know you're thinking "What? Support a support?" YES, do just that.

Champions: Alistar, Taric and Kayle

Why?

Alistar:

Think of this situation. You use your lantern to bring him close, he then does a flash head-butt on their ADC (Who is closer than they should be because they didn't expect a flying Alistar) BUT Alistar has a heal which increases Thresh's sustain ridiculously. And last but not least his CC(Q) is over kill on any support or ADC who comes too close.

Taric: Same points with Alistar although you can easily get him into the fight and switch with him if you are out of position with your Lantern.

Kayle: Shares much of the same point as the above BUT her damage is more outrageous than Taric's gems and if she gets the 'gank' instead she is not terribly bad at snowballing.

In order of best synergy: Kayle, Alistar then Taric.

Thresh's team fights should go the same way he deals with the lane phase champions. Focus on their ADC (Or who ever needs focused) like they were only champion their. Q them to get them close, Ult as soon as their in range and E them to either pull them forward or push them away. BUT always use the lantern to buff your team mates first. :)

Pros/Cons

Pros:
Unbelievably tanky.
Outrageous damage.
Farm is twice as rewarding.
Brilliant initiate.
Can, if played well, beat the odds(2 v 1,3 v 1, etc).

Cons:
Requires good aim to gank.
Very bad sustain if solo.
Incredibly easier to gank earlier game.
Very farm dependent.

Feel free to use and abuse this guide as it is but a base and I have only played Thresh once but looking over his wiki page I felt this build would work (One custom where I went 36/5/8). Make any changes to this guide you would like and I would love to hear what changes you think would be good and any good games you have with him. Here is my custom - http://www.leaguereplays.com/replays/match/2733701/

- Questalace