I usually start with Shulk or Megaman. After seeing a character with a reflector and having the salt buildup from playing Megaman, it's usually Shulk. After getting bored, I bring either Mac or Ike (but Ike always on 2v2) out. I attempt Ganon and Palutena at random and fail terribly. I normally stay around for many matches, but leave after getting curbstomped by a much better player.
The only times I'll quit are under severe lag, by intentional SDs.
In mirror matches, I'll taunt. If my opponent taunts while I approach, I stop and taunt. Taunting after kills usually occurs after they taunt the kill or we play for a while.