The code to unlock the door at the top of the stairs in the Delta Beta frat house is "PICASSO".
Easy lockpicking
When you need to lockpick a door (most likely a difficult one), get to the final rod. When you do, make sure the pin is stuck. Before the pin gets unstuck, shake the Wiimote up and down very quickly. The pin should go directly through the rod and into the hole at the end. Note: This does not always work.
Hacking the computer for dynamite ingredients
Use the code "EINSTEIN" to hack into the computer and get the ingredients for dynamite. Note: When you break the soda machine in the basement (first level) of the hospital, keep the soda. It is the last ingredient you will need.
Hacking the door outside of the Delta-Theta-Gamma Party
Use the code "MOZART" to get in while playing as Mei. This will be the first door you discover. To find it, have Mei search with the decryption device.
Hacking the door to get to Jun
Use the code "FREUD" to open the door and get to Jun. This will be the second door you discover.
How to open the door after you pass the game
After you see the credits the first time don't think its over because its not. Once the credits are over you're going to see a clip and after your finished with that clip run to the house and run away from the monsters. Then once you are in the place were you first sight the professor find the dead guy and get the bat, medallion, and the flare gun. Then put both of the medallions onto the door and connect the lines to each other. This is going to take a while but you will get it.
Safe code
The code to the safe is "1873". You can find it on the desk in the room you enter from the window. Examine it closely with the woman.