What I mean by that is what do you need to do,The one thing on any of your characters,Not just roleplay wise.It could be killing any races that you don't like.Or always joining the same guild.Or always the same agenda.anything.Mine would be me ALWAYS using archery,crossbows or bows.Any sort of that fighting style is molded into my characters.
My mage used the bound bow.
My warrior used the dwarven enhanced crossbow.
My thief used the dwarven black bow of fate.
And my main charcter uses the daedric bow.
What's yours?
Every single time I start a new game I have to get really good gear as fast as I can. On one of my characters I was wearing full Dwarven armor by the time I went to speak to Jarl Balgruuf for the first time. And the only reason I was wearing Dwarven was because I was holding myself back. I could have easily gotten ebony armor. XD
I always have to make my characters change some of their appearance throughout time. I take them to the sculptor in Riften to show some aging or experience. Maybe add some scars, some dirt on their face, longer hair and beard, that kind of thing. I feel it really adds to the whole experience. For example, I've been playing the Clever Man build with a Nord who went from middle aged with little facial hair to a gray haired old man with a huge beard. It's fun!