The one situation I'm thinking of right now, though, is when you're giving your kid a bottle.
I just bought a new set of bottles. (Playtex Ventaire 3-packs. The kid takes 8 oz. a couple of times a day and 6 oz. the other times, so I went ahead and got all 9 oz. bottles this round.)
It turns out the nipples are all Stage 2, with larger openings and higher flow rates. The kid could handle it most of the time, but had to catch her breath a lot, too. POINT ONE: CHECK THE SIZE/FLOW RATE
So I go out and buy a few packs of Stage 1 nipples, her normal speed, and her evening bottle nearly drives her crazy. POINT TWO: CHECK THAT THE OPENING'S OPEN. TWEAK IT OR USE A PIN TO OPEN IT.