Assuming you mean the winter slow time for residential.
Marketing should be done at regular intervals to be effective. That being said I am terrible at sending out reminder cards when Im busy, so that would be the first thing I would do is catch up on that. Even if the customer doesnt need their carpet done right now I have had a lot of them hold on to the reminder card until they do which may be months later.
Also once a year I completely empty the van and go through every item and clean and do any maintenance or repairs on it.
Other than that, at my age my body needs a rest so I dont mind a day or two off until it warms up again.
when your business is on the slow, get your butt on the go
go , check every piece of equipment that you own,
go do maintenance services on all of your equipment
go check and maintain your work van/truck/vehicle
go check all of your emails and label all receipts
go into your office and straighten and organize any paper work
go check and replenish your chemical stock and inventory
go and be thankful, thank the Lord, praise him and trust in him that all will be ok