| Well, that depends. If you kept the default keyboard controls, holding down CTRL will send you into sneak mode (NOTE: you'll only go into sneak MODE. This does NOT guarentee that you won't still be seen, especially if your sneak skill isn't very high!). However, if you've modified your keyboard controls (like me), then the key you press may be different. Check out "Controls" in the options menu (I think it's the options menu, anyway...) | 
Linear Mode
