In the hotel lobby after entering the main doors, you are expected to walk up either of the two staircases and have the stairs fall out from under you. If you jump and crouch over this part of the staircase, you will instead pass over the trigger that sucks you downward and instead get a small boost forwards to the 2nd floor. This skips the basement section of the quest.
In version 1.1, you can enter The Asylum for the first time and then leave. You can then complete the Ocean Hotel quest and return to The Asylum. Jeanette will now have the pendant conversation with you instead of her introduction on the floor of the nightclub and then go upstairs to argue with her sister.
After returning from the Jeanette pendant conversion or after completing the painting slashing quest, you can skip going up the elevator by going to the 2nd floor and crouch jumping into the roof. This will hitbox shift you into Therese's conversation, which automatically draws you into her because she is mad. You still have to ride the elevator down.
Normally to obtain the 2nd snuff tape, you need to speak with Issac and view the 2nd tape, speak with Flynn at the Sinbin for the tape information, pickup the phone outside the convenience store and talk to Andrei, then enter the Lone Star Hotel and enter the hotel room to obtain the key for the backroom of the Netcafe.
You can skip all of that by getting stuck in back office entry door and save/load clipping upwards to the 2nd floor.
After fighting Andrei in Hollywood, you are supposed to go through the warrens to the Nosferatu hideout. This is notoriously one of the most difficult and confusing parts of the game. However, there is a room leading back out to a section of the Hollywood sewers that was previously inaccessible. Part of that section has another door that leads to a deeper part of the warrens. By looking at this door from the right angle, you can open it from the other side. This will skip the first 2 levels of the warrens.
Upon entering the 3rd warren's level, the game will assume that because you are entering this are for the first time, it must play the cutscene that begins after completing the 2nd warrens level, thus warping you to the level's natural spawn point.
In Ming Xiao's Elysium, you can jump on half of a tree and then a lamp to then crouch jump on top of the roof to go out of bounds. You can then enter an area behind the Elysium that you are supposed to enter later when confronting Ming Xiao.