The key with footstraps is to oppose the rig:

Rig forwards - your weight back = being able to un-weight your front foot and get it into the footstrap
Rig back - your weight forwards = being able to un-weight your back foot and get it into the footstrap

This will really help stop the board loosing speed & turning into the wind which is usually the main cause for not being able to get into the footstraps.

Hope it helps & if you ever need any help just give us a call at Poole Windsurfing (01202 237247) www.poolewindsurfing.co.ukand we can run through whatever it is you are stuck with.