On new construction i mount all boxes & brackets for keypads data speakers tv's whatever. After the locations are signed off on i drill my floor to floor paths from the top floor to the head end.then i begin drilling paths towards rooms then finally paths to locations. Then i put in any hooks and hangers and pull all my cable. I strap it in place at the device so it cant get lost in the wall an di start banging in protection plates to keep drywall screws out of my bundles. I work my way from the top floor down pulling bundles neat and securing them and finally at the head end i try to plan out where the racks will be and pull all cat5's to 1 spot, speaker cable to another etc.

To be honest i dont really care about keeping the lengths the same at the head end as long as the shortest one is long enough im happy. If you do the math its better to waste 10 feet of cable than spend an hour each day trying to keep cables the same length. At trim out i cut them all down anyway.

I always pull from the room location to the head end. Since the head end is typically in the basement gravity is on my side :). Also.. its easier to look around a room and make sure all your wires are in place vs trying to determine it from the head end.