Most monday evenings I run a two hour session on BBO in the Beginners & Intermediates Lounge (BIL). I started these about three years ago when Wayne (sceptic) asked me to be his mentor (through the club and Fifth Chair Foundation) and we have been doing them ever since.
I dislike being called a teacher. I believe a teacher is someone who has a plan of action, prepares properly and seeks to deliver continuous improvement. All I really do is share some thoughts about how I think people should play the game and deliver some 'expert' perspectives.
Has Wayne improved? He is certainly more confident in both playing and asking questions, he is happy to play with more advanced players and seems to be enjoying the sessions. He probably needs a proper teacher to help with play and defence but we muddle through.
I have the utmost admiration for all the professional teachers on BBO, both those that provide their services for free and those who charge. Occasionally I do prepare for a specific subject and it is extremely time consuming, but normally I will either use hands that I have previously played or just use random hands - it is surprising how good random hands are!
Our sessions are public affairs and we generally get an audience of 30-50 people, from all corners of the world. The kibitzers are encouraged to play and contribute to the discussions, which does lead to a more fruitful session. In particular it is interesting to contrast the different teaching styles around the world: for example, in the USA weak 2 openers tend to be very sound with a good quality suit and values; in Europe, weak 2 openers tend not to worry about suit quality and they can be a lot weaker - important to know what you play with a pickup partner.