Heuchera

[Mags22]

When is the best time to take cuttings off, now or springtime?

[woofgang]

spring is best, you can do it later but I think now might be a bit late. Now is a good time to divide the plants though, like other perennials.
http://www.gardenguides.com/89519-propagate-heuchera.html

[Chipchopper]

I agree that spring time is best but if you have well established plants, you could try a few now, to experiment.

Look for surface runners and cut a piece off that has a bunch of small plantlets at the end of the runner (stolon).

Separate the plantlets, one by one, removing any old stragly leaves, then pot them up individually into 3 inch pots with potting compost containing John Inis.

Keep well watered and keep an eye out for Heuchera rust on the under sides of leaves.