What zone are you in?

My mums outside are already growing, I'm in zone 8. I am also able to keep mums in ground or in pot, during the whole year since I'm in zone 8.

I'm in Zone 6A. It's still cold here.

I do the same thing. Some may not survive. Just wait till June or so and some will start growing when it warms.

Once it warms should I put them in sun or shade? Should I cut them when I put them out?

I would put them out in full sun once lows get past 40F. I cut them leaving a couple of inches of the stems attached. They will fall off once it starts growing. I leave bit of the stem for a bit of protection from jumping squirrels and such.