M.G.
It depends if your housekeeper is from an agency or an individual worker. When I went with an agency, they have a set number of things within a limited amount of time to do it so there was not much I needed to tell them because they won't do anything outside their list. My current housekeeper, however, is independent, so she would do little things like clean out the fridge or water plants if I asked.
It is addictive!!! My husband got a pay cut and I had to cut her hours but I basically limited my other luxuries such as movies, dining out, cable, etc because I'd rather pay her to help me with my house! It's a sanity saver!
On a less pleasant note, I did get someone who stole from my house once so I would keep any valuables/cash/jewelry out of sight to resist temptation.