User blog comment:Fistful of Force/You don't always have to focus the ADC first./@comment-3275908-20120816082228

For me, it always depends on which carry has the more damaging build.

For example, I'm bottom lane support Leona and my ADC and I have been supressing the enemy Graves the entire early game. Keeping him from farm and killing him several times. By the time it gets to mid game where the team fights happen, he barely has tier 2 boots, a Doran's Blade, and a Zeal and he's underleveled. But the enemy Gragas has been wrecking our mid lane pretty hard, so we decide to focus him down first at the beginning of every team fight.

In rare cases, I've seen my mid and my bottom do well, but top gets crushed so we have a snowballing Darius, Akali, or Irelia on our hands, so we try and focus him/her down.

In the end, the champ with the best build (sans the tank) is usually the one you want to target.

Additionally, as a interesting bit of strategy that won't often come into play but it's good to note anyway, is if the one getting the awesome build is notoriously difficult to kill (Anivia, Kassadin, Corki, Fizz, Gangplank, etc. etc.), focus the entire rest of the team before dealing with the big guy. Gank them, 5v1 them, harass them... and their builds will be so crappy, you leave the big dude all alone to deal with your team.