For the creative side I would recommend trying out all kinds of things. Should your player be able to get stuck/into a dead end? Will players play once or many times. Can you "win" your game or is it more of a narrative? How do you want the player to feel!
For some more specific ideas, think about how your game branches. Branching and decisions in games are far trickier than they might appear. Too subtle and the player misses the choice entirely. Too in your face and they become boring ("kill the baby" vs "save the baby", gee I wonder which one takes me down the evil path)
Also, merely asking a question or giving a choice can influence the player. If you ask "who is the killer?" and give a list of suspects, one of them must have done it, even if the player never considered it. The question also assumes the player knows there was a murder and gives that away if they hadn't worked it out yet.