if it's post lights, 12-14ft high a rug has worked for us, if it's a pole light with glass lense around it, steves idea has worked for us, if its a pole light with a cupped lense...those are more difficult to cover temporarily but they are usually not as big of an issue because they are using the lense to direct the light. on occasion we have been able to locate the photo cell, illuminate it, and get the light to turn off long enough to get the shot.
C.O.L.D. (Certified Outdoor Lighting Designer)#1112
C.L.V.L.T. (Certified Low Voltage Lighting Technician)#0639