Wear a normal long tie, with a nice double-windsor knot. The front part of the hood is normally a thin strip, and can be placed under the tie... to keep it in place...

I will try to see if I have a pic (sorry, my own graduation was before the general profusion of digital cams, so if I do have a pic here I'll have to scan it.

(it's difficult to explain...) And, again, it might depend on the academic dress of your particular University.

Cheers,

Michael