The day of the week and time of day is important. Inbound to Manhasset you want to be crossing the Throgs Neck NLT 2pm on a weekday. Weekend mornings especially Sunday are the best of the daylight hours to travel on LI.
Outbound to the George Washington Bridge is best before 2pm on weekdays. I think trucks/trailers are upper level only on the bridge. There is no toll on the GWB westbound. On Sundays one must be careful of the Jets/Giants game time if at home in the Meadowlands south of the GWB. That must be avoided completely.
Have your EZ Pass loaded up w $$$. If it's raining go earlier. If you miss the the TNB continue on to the Whitestone Bridge which is a couple miles west of the TNB. DO NOT GET ON ANY HIGHWAY THAT IS NAMED A PARKWAY. They run parallel to both 95 and 495. Take your time, remain calm, and look over the map in detail beforehand.