Hi, I've just been reading all about weaning over on kellymom.com there are some great articles about it there which are worth a read.
With DS1, I expressed regularly in the early days and he happily took a bottle. When he turned seven months, I started introducing formula in preparation for going to work at about 9 months. A week before going back to work, he gave up the breast altogether. At a year, we switched to cows milk.
With DS2, he didn't take to bottles very well and having done quite a lot more reading about BF by this point, I knew that I didn't need to switch to formula. I went back to work when DS2 was 9 months and did no 'preparation' at all...just handed him over and hoped. Fortunately, he happily takes water at nursery but feeds from the breast when he's with me. My boobs seem to deliver whenever he wants it, which is amazing. At first he fed more through the night but we co-sleep so that's easy enough.
At the weekends he BF's during the day too, but not during the week.
Having said all of this, all babies are different but I'd say that if you read something and it feels wrong, don't do it - you'll know best what suits both you and baby.
Sorry for mega-waffle and good luck!