I've been keeping them in a shoebox-sized plastic container with soil and wood chips and a thick layer of carboard over the top. I sprinkle a bit of fish food under the cardboard. They've been in my basement all winter, around 15C. There is no natural light down there, but I adjust the timer on the lights to give a shorter cycle in winter.
Daniel, I have newt eggs here, but I take that for granted. This is something unexpected! You better congratulate me!
Becky - when you say you get them everywhere, do you mean find them outdoors, or find them for sale? I have plenty of them outdoors in summer as well, anytime I have the patience to go rummage about the garden for them. But what I really need is TINY ones (to feed small terrestrial newts). That was my motivation for trying to culture them. Also, I prefer the less-crusty less-rolly variety of woodlice, so I selected those for my culture.