My lab has a Helmer plasma freezer and I would like to know what other facilities use to label the different drawers of plasma.

Nothing special; tape and permanent marker. 
Works best if draw dry and at room temp.

We printed on cardstock, affixed with self-laminating sheets, and labeled with the freezer at ambient temperature.

We didn't label the freezer drawers.  But we do have a job aid hanging on the door with the freezer contents (by drawer).

It makes it much easer if/when you move your contents around.

sandra