Paraphrenalia
Some people like to have certain music playing, or have incense or a scented candle burning, or crystals around, or wear a special garment, or more likely, have a special ‘casting cloth’ for divining on. This is a matter of personal preference, not a requirement. If such things help you focus and get in a divining state of mind, then use them. I find the right state of mind is far more important for divining than having the right accessories.
Frequency
Some divination methods, such as the yes-and-no stones, or the pendulum, you have to ask a great number of questions in order to get a discernable picture of the issue you’re asking about, and that is fine. But for most divination methods, my general rule of thumb is: no more than three questions in one divining session. At most, no more than one divining session in a day for the same inquirer (the traditional word for ‘inquirer’ is ‘querent’ but I’ve found some people are uncomfortable with that word).
Like I said earlier, I’ve found each divination tool has its own ‘spirit’ or personality to it, and you don’t want to tax that spirit’s patience. In fact, the I Ching will even tell you when you ask it a third question, “You are becoming impatient. I do not instruct the impatient.” Just as you wouldn’t permit a young child to pepper a guest with many questions, do not yourself or let anybody you’re doing a reading for, pepper the Spirits with a whole long string of questions. Again, it’s a matter of courtesy to the Spirits.