you can print out keycodes, characters, specials, etc in the key event handler script.
print(keycode, character)
I think arrow keys are eKeyLeft, eKeyRight, eKeyUp, eKeyDown because they are special characters just like eKeyEscape. They might require Arrow on the end though like eKeyLeftArrow - I forget. You can also check if they are x keycode instead too.
Regular characters (letters & numbers) you can check with...
if character == "w" then
-- do something
elseif character == "a" then
-- do something
elseif character == "s" then
-- do something
elseif character == "d" then
-- do something
end