Good Afternoon, Luigi,
Ditto on the flash meter suggestion. If circumstances permit, it can be helpful to shoot the scene first with B & W film of the same speed as your color film. Processing a batch of negatives takes less than an hour. If you don't normally process sheet film but your camera takes a roll film back, that may also be an option with B & W. Judging negatives is a bit tricky, but contact sheets don't take long to make if necessary. After a while, experience will begin to be very helpful.
Konical