
It seems that there are dozens of common variations in how one plays Riichi Mahjong (and, likely, dozens more that are played locally that don't make it into the typical Riichi references and various Mahjong books in print).
Here is the rule-set I tend to use:
General Rules
Tonpuusen (East-Only round as opposed to the more typical Hanchan East-South rounds - I prefer my games a little more luck-based and a bit more aggressive offensively and I get this with East-only matches)
1 Han Minimum
Agari Yame: Yes (you can quit when you win the final hand and are ahead)
Hakoware Tobi: Yes (Any player falling below zero points ends the game)
No-Ten Bappu : 3000 points (penalty points for a drawn hand by the players not ready)
Ta Cha Hou: Allowed (the 'head bump' rule which allows 2 players to Ron simultaneously and both are paid)
I have no feeling for 3 player simultaneous Ron - I've not seen it happen so haven't thought about it. I suspect I'd go for a draw.
I don't know what it's called in Japanese, but I prefer that the seat winds only stay if the Oya (Dealer/East) wins (i.e. on a draw seat winds will rotate).
Dora Rules
Ura Dora: Yes (the underneath/underside Dora for those who Reach and win)
Kan Dora: Yes (new dora indicator flipped with each Kan)
Kan Ura Dora: Yes (the underneath/underside Dora below the extra Kan dora)
Akadora: Yes (Red 5's as follows: 2 in Pin, 1 in Sou, 1 in Wan)
Yaku and Ready Rules
Open Tanyao: Yes (all-simples can be open)
Tsumo Pinfu: Yes (you can self-draw a 'Peace' hand and forgo the 2 points you would normally get for that)
Daburu Riichi: Yes (you get an extra yaku for declaring Reach on your first turn)
Riichi Ippatsu: Yes (you get an extra yaku for going out within 1 turn of declaring Reach)
Nagashi Mangan: Mangan (5 Han) Limit Hand (all Terminal and Honour discards, no player takes any of these and the game otherwise come to a draw)
Kazoe Yakuman: Yes (13 Han). This allows you to get to the maximum Yakuman limit by getting your han value (with Dora, etc) up to 13 or more.
Dai Sharin Yakuman: Counts as Yakuman hand ("Big Wheels" - I'm all for more Yakuman hands at least until I get one!)
I realize these rules aren't exhaustive but those are the ones that come to mind when I play and when I explain the game.
So... how do you play?!