Once you have come up with an approximate figure for the ideal altitude, you need to take regulations into consideration. Under VFR conditions, you need to fly at an even thousand plus 500 when heading in a westerly direction and an odd thousand plus 500 when heading east. If your route directs you close to a northerly or southerly heading, be aware that opposing traffic could be at the same altitude. And while you won't know for sure where the clouds are until you begin your flight, you need to plan to stay at least 500 feet below existing or forecast cloud layers, while staying well clear of obstacles. If there is any question whether you can achieve this, cancel your flight. I would not recommend flying VFR on top unless you are IFR current and can pick up a clearance en route.