You can play him with some fun specs (AD carry, AP nuker), but I've seen him do best as a tanky support. Build up those aura items (Aegis, FH, Zeke's, Abyssal, Randuins, etc.) and encourage your team to fight as a group as much as possible to maximise the benefit.
In a big fight, try to save your stun to peel for your squishies (eg. if an assassin or bruiser manages to jump on them). Between your protection and auras, your team will have a big advantage. If you're racking up the assists, it means you're doing it right!