The guide-line for promotion to Bench Ozeki is a score of 30 or more wins over three consecutive bashos. The second basho of which, the Bench rikishi in question, should ideally be ranked in Sanyaku (either Komusubi or Sekiwake), and the third basho at Sekiwake. In the times when a new Ozeki is needed, the guidelines will become more lenient.
Bench Ozeki demotion
On each day of the Bench Basho, you will be matched against another Bench rikishi. At the start of the basho, you will be scheduled against Bench rikishi with a similar rank to you. As the basho progresses, you may (or not - it is not always possible to do so!) be matched against Bench rikishi with a similar record to you.
Those Bench rikishi ranked in Sanyaku and the top Maegashira ranks will, normally all face-off against each other during the basho. On the last day, the last three matches will normally feature the two topped ranked bench rikishi against each other, the 3rd and 4th ranked, and the 5th and 6th ranked, regardless of their records to that point.
In short, the Bench sumo Torikumi will reflect as close as possible the Torikumi used in real sumo. The Torikumi gyoji/shimpan will endeavour to send out each day's bench torikumi two days in advance, and before the equivalent real Torikumi is announced.
Bench Yokozuna promotion
A Bench Yokozuna hopeful must have won at least one Bench Makunouchi Yusho at some stage in the past. The general guidelines are that the normal minimum requirement for promotion should be two consecutive Jun-Yushos, whilst at the rank of Ozeki (provided that they have previously won a Makunouchi Yusho.)
The Rijicho (currently Jejima),will ask the chair of the Bench Sumo Yokozuna Deliberation Council to convene a meeting. In general, this will be after an Ozeki has just won a Yusho, or good Jun-Yusho.
The Bench Sumo Yokozuna Deliberation Council currently consists of Marushiki (as the esteemed chair), Hakaso, Leonishiki, Sherlockiama and Sakana.