When you do zazen, find a quiet place where you can sit without disturbances. It should be neither too dark nor too bright, warm in the winter and cool in the summer. The sitting place should be neat and clean.
If possible, a statue of Manjushri Bodhisattva should be enshrined in the room. If there is none available, any statue or painting of a Buddha or a Bodhisattva is fine. Also, when possible, place an offering of flowers on the altar and burn incense.