Sitting properly is an important part of your effort to prevent sciatica. Your hips and your knees should be level when you sit. If you're seated at a desk, your feet should be flat on the floor, and your elbows should be bent at right angles. When selecting a chair, choose one with adequate support for your lower back. A swivel base and arm rests are also recommended. A properly placed rolled-up towel or small pillow can help you keep the natural curves of your spine.