I'm looking for good information on how to care for them and identify them as they weren't labelled. I guess that it's not as simple a giving them very little water?
If anyone knows a good website or book, I'd be grateful.
Edit: Typo
Can’t help too much with ID, but I can suggest a few things. First - as much sun as possible! If possible, south-facing windows are best. North are worst. Ideally you could put them in front of the curtain - behind likely won’t be enough! Watering-wise, water when the soil is completely dry - cacti are very easy to overwater!