Whenever I tank, if I'm with a healer I know I will always do large pulls if I know they can handle it.

If it's with complete strangers, I tend to do the first pull as a stress test of sorts, and pull two groups. If things go super easy, will do larger. If it's okay, will keep that way. And if it goes to sh*t...small pulls from there on out.

Just need to read your party, and see how they are with the pulls as you go.

I'm with the OP on the first time in a dungeon and only doing small pulls to learn it(such as what monsters have skills that should be stunned).