I've recently reached the point where I'm starting to feel confident in my laning and small skirmish play, but in most games I've noticed the quality of my playing declines as the game stretches into the team-fighting phase (in normal queue this seems to usually be around when champs hit levels 9-10+). Teamfights can start and finish so quickly in this game, plans definitely fail to survive encountering the enemy. I was wondering, what tips other players have for staying focused on the right target, properly using skills, etc.?

Well, it really depends on what champion you're playing. If you're playing annie, let someone more tankier initiate and you can drop your tibbers/incinerate in the middle, hitting every really. But lets say you're playing someone more focus heavy like Lee Sin. Quote "Don't be Julias ****ing Caesar, Initiate!" Focus someone, your team will most likely follow you to whoever you hit, because you initiated the fight, if you're not the one who initiated just follow the person who did, that's what works.

Pretty much you have to realize that different types of characters, and even different characters of the same type, are more effective at different aspects of the game including fights. Thi being said you need to know your characters role in a fight, and the strengths of your character vs other characters. ie. are you playing a mage? (anivia) so yes.. ok your champion is skilled at bursting down targets.. you wanna aim down their carry. in another example, are u playing a mage? (veigar) yes, veigar is skilled at taking down other mages (ulti) and has the burst to take down carries... in this case u have to ask urself which is the priority target. Maybe the ryze on the other team is crazy fed and your team needs to down him before u down the gangplank?

After u have learned what your role is u also have to consider ur cc capabilities... veigar has a huge stun capability.. that even if the enemy team doesn't run out to stun themselves u have them all on lock for aoe's little things like that.

It is good to focus on a single target, but don't forget that your allies might need you to help too. I've seen way too many allies chase "high priority" targets that turned out to be unkillable and ignore others that could easily have been killed with some teamwork.

Don't get tunnel vision. It's more important that your team works together to kill a single target than necessarily have one person dead.