If your sheets are a high tread count, made from silk or other expensive materials you need to wash them in the gentle cycle without any other clothing. The gentle cycle is not as rough as the normal cycle. Your sheets will still come out looking clean without all the wear and tear.
Choose a mild detergent and fabric softener to wash your bedding. A little bit goes a long way when it comes to soap. Only put a small capful into your washing machine. Fabric softener will help your sheets maintain a soft feel. You can buy liquid fabric softener or sheets to put in the dryer. Set your dryer on low when washing expensive sheets. If you live in a mild climate you can also experience ultimate freshness by hanging your sheets outside to dry on a clothing line.
Do not mix white sheets with blue or dark colors. Wash them separately and avoid using too much bleach on white sheets. Bleach does whiten sheets, but too much bleach over time can break down fabric. If you need to brighten your sheets every now and then add bleach, but do not do this every time and only use bleach for white sheets.