Ash HN: How you avoid butt-dialing?

I just dialed a friend 3 times in a row by accident in the period of 10 minutes. What is your way to avoid butt-dialing, and how well does it work?

Suggestions I've read about are "just lock your phone", for Android: unlock pattern, Call Confirm app, Tiny Call Confirm + app, iPhone and others: pin lock.

I still think having a clamshell phone was the best way to avoid butt-dialing, though.