I want to have my butt centered on the widest part of the saddle and be able to comfortably reach the handlebars while having my back at a 45 degree angle. When riding, having warmed up for 10 minutes, I want the saddle to handlebar distance to feel right and by that I mean that I do not feel the need to slide further back or further forward to have support from the seat and be able to pedal effectively.
What is also important for me is the seat angle and usually I have it set at a 4 degree down angle from being perfectly horizontal but it varies by seat. I take a hex wrench and make adjustments as I ride a section with flats and hills.
So I adjust seat height first and then make a preliminary seat position of 24 inches from butt center to the top of the stem, and then I ride and adjust, ride and adjust until it is right for me. Doing this adjustment sitting still on a bike in a shop is not the best way to do this.
Race cars have their suspensions tuned in much the same manner where the driver takes it out on the race course and then based on what the driver reports the mechanics will make adjustment and this process is repeated again and again. And it is not done with the car up on a rack but with it out on the road.