If baby chokes during feedings, you probably have an overactive let-down or an oversupply of milk. So congrats — too much milk is certainly better than not enough. To keep baby from choking and sputtering in the future (and to prevent other issues that can come with an oversupply, like gas or colic symptoms), you'll need to tame your supply a little. To do this, try nursing on only one breast per feeding. If baby is already taking only one breast per feeding, try using only one breast per four-hour period. (If the other breast gets uncomfortably full, express a tiny bit of milk for relief.) You should see a reduction in supply — and baby should stop choking — within about a week. Once the choking has stopped, you can resume nursing as normal. (Remember to let baby nurse on the first breast as long as he wants before switching. You may not need to feed from both breasts at every feeding.)
In the meantime, try taking baby off the breast during let-down and letting your milk spray into a towel or burp cloth for a few seconds before latching baby back on. Nursing in a reclined position with baby on top can also help by reducing the speed of your flow.