#1 Enter Party (right after fireworks)

#2 Potion Class (right after meeting ron on the 7th floor)

#3 The trap (when going to the astronomy tower to fight crabe and goyle)

#4 Hufflepuff match (from hospital wing to the quidditch pitch)

make sure for that route that you save and quit as soon as you spawn in the cutscene with ginny talking to you near the hospital wing (it increases harry's speed) otherwise you won't save time with it

#5 Leaving Hogwarts (right after doing the last potion)

For anything else, just use nick by pressing select