Copied from the official quick-reference card from Midnight Obsidians actual copy of the PC version of U4: 

A) Attack 

B) Board ship / Mount horse 

C) Cast (Followed by the number of the character who will do the casting, and then the letter of the spell) 

D) Descend 

E) Enter 

F) Fire a ship's cannons (followed by the direction, broadsides only) 

G) Get Chest 

H) Hole up and camp (may only be used successfully with limited frequency) 

I) Ignite a torch (requires torches from guilds) 

J) Jimmy lock (Followed by the direction of the door) 

K) Klimb (Up by default, use D to descend) 

L) Locate position (Requires sextant from that pirate place)

M) Mix Reagents (Followed by the letter of a reagent, one letter per part, with no seperators. Return mixes them. If I wanted to prepare a Jinx spell with one part of black pearl, one of nightshade, and one of mandrake root, I'd type BNM and then press return. 

N) New order (followed by the numbers of the characters that you want to switch) 

O) Open door (followed by the direction) 

P) Peer at gem (requires a gem)

Q) Quit and Save 

R) Ready a weapon 

S) Search (looks on the ground for unusual items) 

T) Talk (You're going to want to say "name", "job", "health", and "join" to most everyone that you meet, then ask about the things that they mention, particularly the nouns.) 

U) Use (Uses an item found with the search command) 

V) Volume (Toggles sound) 

W) Wear armor 

X) Xit (Exit your horse, ship, etc and continue on foot) 

Y) Yell (Yells "giddyup" or "whoa" to speed/slow your horse) 

Z) Ztats (Displays status)

Thanks go out to Midnight Obsidian for the key layout! -reaper
