Share 'How do you develop a preplan?'

Every tactical book you read or class you attend tells you to have a preplan for your commercial structures but none tell you what you need or how to do it. I'm trying to put some together but I'm not sure the best way to go about it. Do you make a drawing and include some numbers and info? Or do you write some sort of action plan with detail instructions about apparatous placement and tactics? O…