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Tournament takes 15 days and the schedule – torikumi (can mean either a single bout or a daily schedule) – is decided a day ahead, even before the matches happen (so if a wrestler is injured during his bout the previous day, he will still have a scheduled match, and his opponent wins by default). At the start the schedule follows certain established patterns (top wrestlers never start facing each other); later on the schedule is adapted to current performance. Since there's a lot more than 15 wrestlers in a division, they will not all face each other. If a wrestler at the bottom of a division shows very good performance during first 10 days (when he normally wouldn't've faced anyone from the top of the banzuke), he will be scheduled to face other title contenders (to avoid an awkward situation where a wrestler who wasn't expected to win the title wins without having faced top contenders). Also, the yokozuna will face each other during the last day (or the last couple days when there's more than two). If there's more than one wrestler having the same winning score at the top on day 15, they will do extra playoff bout (or bouts if there's more than two).
In general, everything is improvised on spot.
Each win is one point, and – again in an improvised manner – the ranks for the next tournament are decided based on last tournament scores. Since wrestlers usually face other wrestlers ranked around them, there's no weighing of results based on opponents.