At his age, you're right on target by focusing on the cup if he doesn't take the bottle well. There's really no reason why he can't sip from a cup if that's how he prefers to do it. It does take babies some time to get used to the sippy spout, I don't think my DS really drank from it consistently until he was closer to 1. Even then, he still just took dainty little sips. ::)Playing with the sippy is really just his way of figuring it out, so letting him explore it might help him learn how to use it. As for amounts, he should be taking around 24 oz total per day. Obviously, while you're in the process of dropping feeds, you'll have to kind of guesstimate a bit. Location, you'll probably have to take cues from your DS on that one. Using the bf location can work both ways...the association with nursing can either cause your DS to say "oh yeah, we eat here" and take the cup or it can cause him to hold out for nursing. Then again, it can have no effect at all! HTH!
