Skidoodle - I've been told that if you start expressing too early, it can interfere with you producing the correct amount of milk at the correct times. So at the start, while your poor boobs are trying to figure out what the heck is going on, it's best to confuse them as little as possible. Later on, once you and your boobs know more or less what you're doing, you can start expressing. Of course if you have babies who can't feed from the breast for whatever reason, you have to express instead.
I found that I couldn't express to start with - nothing came out! Not sure if it was the pump or my supply or what. It was only once I got settled into feeding, and tried again when I knew I was really full of milk that I managed to get expressing sucessfully.
Oooh, and just to add to the fun and panic, I remembered something else last night that they don't really warn you about beforehand - the after-pains as your uterus shrinks again. I don't remember if it was the next day or more after DD was born, but I was curled up on the bed in agony, sure that I was going though labour all over again!! I'd had a few pains before that (and, unfortunately, mostly while feeding DD - feeding causes shrinkage contractions) but that one day was terrible! I nearly had my mum call the mw, I literally couldn't move!
Hmmmmmm, anyone would think I want to put you ladies off bf-ing, which really isn't true cos it's lovely! Just best to know what's in store, I think.
Perhaps I should shut up before I put you all off having babies completely!!