Duo queue with someone you trust with.
If you know you're awesome at playing tanks and initiating, stick with heroes that do just that and have backups.
For when I play ranked, I usually go tanky DPS or tanks. I can lane or jungle with tanks or tanky dps. I can also play caster as back up. I know I'm not the greatest at AD carries so I usually avoid that role. My partner on the other hand is awesome at playing alot of different carries so that actually fills my weakness and we have two core components of the team covered. Also, if you duo queue, one of you MUST absolutely get a solo lane.
As for carries, I would add Kass +Urgot + Akali to Minuss' list and Irelia + Ryze to Tanky DPS.
And to me, usually the better junglers are Noc + Udyr + Rammus + Shaco + Nunu(doesn't have good endgame though)
Also, protip: Please don't rush stupid items like Thornmail or Lichbane. It's just that bad.