If you are visiting another school as a representative of your own school, a phone call should be made ahead of time or in the old days a card stating your lineage and a gift as a friendly gesture. Bottom line when I talk about protocol, the school that you are visiting should know that it is a friendly visit and not an act of challenge (unless that is your intention then it is a different story lol)
Once you are in the school, should pay respect to the school alter. Don't touch any weapon. Don't step onto the training floor without an invitation or start touching any of the school equipments. If there are students training, keep your opinion to yourself etc. Just use common sense.
The most important of all, make sure that the school you are visiting does not have any conflict with your own school in the past. It is always a good idea to check with your own sifu first before visiting someone else school. There might have been history in the past that you are not aware of.

Dixon