Bring the question that is actually on your mind
A useful consultation begins with a real question. It can be broad, but it should belong to your life rather than to what you think you are expected to ask.
If several concerns are connected, write them down and decide which one needs attention first. This gives the conversation enough room to be careful.
Bring the details that create context
For Jyothishya, bring your date, time and place of birth as accurately as they are known. For Vastu, plans, sketches, photographs and directions are more useful than a description from memory.
If the question involves an event, move, project or decision, note the dates and practical limits that matter. You do not need to prepare a long history.
You do not need special vocabulary
Come as you are. A consultation should explain its reasoning in language you can follow. Ask whenever a term or connection is unclear.
It can also help to leave a little unhurried time after the conversation. Notes often make more sense when you can read them again quietly.