While trying to save Nevil on the night after the first day, you need to get past Prefects in the entrance hall. After the Prefect in front of you walks down the small stairway, cast Flipendo straight across. All of the Prefects will go toward it, and stay for a few seconds. When this happens, quickly run toward the door. Note: A few Prefects will come up the stairs.
When in the Slythern common room and the Prefects are looking for you. If catch you with the Leg Locker Curse and are saying to get out and you start over, you do not lose House Points.
When you are in the entrance hall and have just come in and are following the Prefect, he will go across the stairs and not down. When he goes across, go to the railing and Flipendo near your hourglass. The two Prefects will go to the hourglass and you can walk out the door.
While in the library annex, to get past Prefects hide in the dark areas. Walk in the dark area to get past them.
When sneaking around at night (especially in the library), the first time you get caught a few House Points will be deducted. More House Points will be deducted if you get caught again. If you get caught after the second time, House Points will not be deducted.
The Right Analog-stick is very useful when you are sneaking to look to your sides. This especially helps when trying to get books for Hermione, and when you turn into Goyle and talk to Draco.
