This was writen as a handout for Chado Norway's studygroup.
Tea is very formal activity. During keiko (practice), as well as during events, this is shown in the way we dress. I have separated the discussion into western clothing (youfuku) and Japanese (kimono), but first some general comments.
Your clothing should be clean and whole, what ever else it might or might not be. It should not be too flashy in design or color.
In tea, one always use white socks. This is to show that we have taken care to put on clean clothing for the occasion.
Futher note that one does not use any jewellery in a tea room. This also includes wrist watches, and similar items.
It is generally not a problem to use western clothing for tea. However, there are a few things one should keep in mind.
Tabi are for instance not considered appropriate for western clothing, one should use normal socks.
It all depends on what kind of event, but to speak generally, a suit is best.
For men a tie is appropriate.
For ladies it is important to note that a skirt has to go past your knees, otherwise seiza might be very embarrassing.
Even when wearing a suit, white socks are used. It is a good idea to wear normal socks with the suit, and change to white socks when you arrive at the location. If there is no appropriate place to change, it is not uncommon to pull a pair of white socks over your regular socks.
It is best if your trousers or skirt are made from a soft fabric that will not cause you discomfort while sittitng in seiza. Also try to avoid clothing with metal fasteners or studs, like most jeans. These may ruin the tatami.
It is also good if your outfit has a belt, since this is where you place your fukusa.
Wearing kimono correctly is an art in itself. I will just mention some general principles here.
As a general principle I would say that any kimono is better for tea than youfuku. This also goes for keiko, as it helps you get a good posture.
The kimono should, if possible, be of silk or polyester that looks like silk, and have at least one mon (family crest) on the back.
Men should as host always wear hakama, and almost always as a guest. It should be a very informal event for you to do away with the hakama.
Ladies should use iromonji (one colored kimono without patterns).
More freedom is given in what kind of kimono one can use, both regarding pattern, and fabric. Ladies should use komon (small picture) kimono, and men do not need hakama.
It might also be possible to use samue (Japanese working clothes) during keiko.
For some of the higher temae it is common to use a more formal kimono while doing keiko.