While we have stickies my quickie take is:
1) Wait till the water is at or just above 60 degrees
2) Clean totally
3) Run FC up to shock level for your CYA level
4) Add 1 quart of 60% Polyquat
5) Wait 48 hours
6) Run FC up to shock level again and close.

In the spring, open after the last ice is gone but before the algae starts growing, if you can.