Level Skip
At the main menu, hold Shift and press Down, Right, Left, Right, Left, Right, Left, Up.

View Next Movie Sequence
At the main menu, hold Shift and press Up, Left, Right, Left, Right, Left, Right, Down.

Next Path
At the gameplay menu, hold Shift and press Left, Right, Up, Down, Left, Right.

Chanting
If the slig guards don't have a clear shot at you, try chanting. Unless there's a robot monitor nearby, You can possess them. Use them to kill other guards and so on.

Mudokons
Before you rescue a large group of Mudokons, make sure that you won't be needing them for anything. To solve several puzzles, you must get three or more Mudokons to work together.

"Wait" or "Work"
Unless otherwise commanded, a blind Mudokon will continue walking in the direction from which he last heard Abe's voice. If you stop walking, he'll amble right past you and into a meat grinder or off a cliff--unless you tell him to "Wait" or "Work."