Stepping up frozen yeast

Been looking around for this answer and can't seem to find something concrete.
I've frozen several 15ml yeast samples that are 15% glycerine. When I go to make a starter, how many steps do I need? I doubt that I'd just tube the thawed tube into 1 liter of starter wort.

quite a bit. When i did it i stepped from around 250ml of 1.035 wort up to 500-600ml of 1.040 to a liter. It took a while because the tubes are so damn small and i didint want any contamination. It depends what strain your using, how good you were when you harvested and how strong your starter is. Your far better taking more steps so you don't stress the yeast and they came out great for me. Careful with sanitiation at first because the cell counts are so low its easy to contaminate them.

Ok, thanks for the answer. Soon as my stir bar comes in I'll give it a go.