It really does depend on which flower you are asking about. Some you cut the foliage back before lifting and dividing others you don't.

If you have no way of knowing what they are I'd compromise and cut them well back but not quite to soil level. Some clumps you can separate easily, some are easier with two forks used back to back and some need chopping with a spade or a good knife. Perhaps you could try to describe the flowers?

A photo of the plant would help,if possible,

Hi, welcome to GoY, if they begin with 'E', they could be Echinacea, in which case they can be divided in either autumn or spring, if you decide to divide in spring, leave the flowered stems for the birds to get the seeds, if you divide them now, cut them to the base, but whichever you choose, you should be aware that they resent a lot of root disturbance, so dig them out with as large a root ball as possible, and a sharp, clean cut, Derek.