When doing the actually dying bit, you will need to cover your working surface with plastic. Something like a plastic table cloth will work fine. You also need to wear old clothes, old shoes, etc. The dyes will stain your clothes, the floor, the walls, the ceiling, etc. So if you are not working outside please be careful. The dyes are harmless to your skin, but if you don't wear rubber gloves you will achieve red, yellow or blue dyed hands, which won't wash off (wears off in a couple of days - but can be a amazingly embarrassing!). Also be ready with the rags to mop up spills. When I mix the dyes I make sure that the caps are on tight and I also wipe the screw top and bottle neck to avoid "capillary action". I have also purloined some of my husband and son's old white socks and cut them down to fit over the bottles, which helps stem accidental leaks!
Hint: there is a product called Reduran, which can be purchased online from Dharma, which removes dye from the skin instantly, so you don't have to suffer "rainbow hand" syndrome!