For example, when the Sensei claps his hands, students should stop practising. It may be that the Sensei has seen someone do something hazardous and wants to correct it before any damage is done. Naturally, it is bad etiquette for anyone other than the Sensei to clap their hands during practice.
There is more to politeness than just the trivia of daily life. I mean, it really doesn’t matter whether or not you consider it polite to raise your little finger when drinking tea. But it does matter that you adopt a serious and respectful approach to the study of a martial art. When you enter the dojo you may be feeling angry after an argument or frustrated after a hard day at work. But for the next two hours, you have to put that behind you. The etiquette of the dojo is one way in which you show yourself prepared for serious practice. It shows both your respect for the art which you are studying and your respect for the people with whom you are practising. If you need a quick overview, see the Dojo Etiquette page on this site.
Different dojos may adopt some slightly different conventions, in particular in regard to bowing in and bowing out of practice. Some dojos, for example, display a picture of the founder of Aikido (O-Sensei) or of the founder of that particular school of Aikido (for example, Tohei Sensei, the founder of Ki Aikido). If a picture is displayed, it is normal to bow to that picture when stepping onto or off the mat. The entire class may also bow towards the picture at the start and end of practice.
This video provides one example of ‘bowing in’ at the start of a class…
Another common point of difference is found in the use of Japanese phrases at the start or end of a lesson. In some dojos, no Japanese is used and the class may simply bow silently to the teacher at the start of a class and either bow silently at the end or bow and say “Thank you, Sensei”. Other dojos (and this is the case at the Hartland dojo) bow in using the phrase “Onegaishimasu” (the pronunciation is, approximately: Oh-ne-guy-shmass) which means “Please” or “Please, let’s begin”. And we end practice by saying, “Domo arigatou gozaimashita” (pronounced: Doe-mow, Arigat-oh, goes-aye-mash-ta) which means, “Thank you very much”. It doesn’t matter if you can’t remember the Japanese phrases. A respectful mumble will suffice at first! J However, if you want to practise your pronunciation, I recommend this site: http://www.aikiweb.com/language/audio.html