Here are two helpful resources:
I would suggest trying lots of calming techniques before feeding, such as rocking, swaying, and skin to skin contact.
*Nurse frequently--smaller, more frequent meals mean more hindmilk for baby and less of a "waterfall" rush from the breast
*Watch the baby, not the clock. Finish the first breast first.
*Try nursing semi-reclined so that the milk flow is working against gravity.
*If baby starts coughing and choking, take him off and allow the milk to spray into a towel. Then latch back on.
*If your milk production is substantial, consider block nursing to slow down production levels. See the links above for more detailed information.
*Call your local LLL Leader for support
*Post in the "too much milk!" section (scroll down the forum listings) for support!