THOU SHALT MAKE THY CONTROL SYSTEM LOGICAL AND FLEXIBLE
Too many times I have played a game in which the save system is disgustingly flawed. Earthworm Jim 2 -- collect three stupidly well-hidden "Pieces of the password" to save. And the save will randomly not work 80% of the time. CRAP. Tomb Raider 3 -- find a Save Crystal. Save it up and use it when the time comes. EH!? And don't even get me started on typewriters and ink ribbons.