The day parade will always start by Splash Mountain and the Night parade will 99% of the time start by the car barn on Main Street. (The only time that this is changed is when they are filming the night parade. If they are filming they will start the night parade by Spalsh so that when they film it on Main Street the castle is behind it...) It is VERY rare that they would start the night parade by Spalsh so bet on it starting on Main Street (the reason is that people like to follow behind the parade, it would be an absolute madhouse to have everyone (try to exit after the parade) walking behind the parade as it headed to Main Street... so it runs towards the back of the park to leave the entrance/exit more accessible...