1. You visit someone or want to ask a question from someone, but you observe that he is busy in some activity. For example, he is reading Quran, or his wird, or purposely sitting in solitude writing, or getting ready to go to sleep,etc.. In summary any activity that your intervention will distract him from and be a source of encumbrance and discomfort, then it will be best to avoid any talk with him at that time. Wait till he is free.
However, if it is regarding something absolutely essential then ask his permission before proceeding.
2. While waiting to meet someone. Do not sit in place or adopt a posture that shows the person you are waiting for him. It will unnecessarily distract him and cause spiritual inattentiveness. You should wait for him at a distant place away from his sight.
3. Do not shake hands with someone whose hands are occupied, and freeing them will be an unpleasant task. Suffice on greeting him with salaam only.
4. Similarly, when visiting a person who is very busy do not wait to be told to be seated. Find an appropriate place and sit.
5. While talking be direct, concise and clear. Do not use slang, elusive or effusive language.
Aadab ul Ma’ashrat page 9-10