Eight ways to keep your home secure while you are away.     Leave blinds open in their usual position. Have mail and packages picked up, forwarded or held by the post office. Lower the sound of your telephone ringer and answering machine so they can't be heard outside. Arrange to have your lawn mowed or your walk shoveled. Stop newspaper deliveries. Ask a friend to pick up "throwaway" newspapers and circulars. Use automatic timers to turn lights on and off in your living room and bedrooms at appropriate times. Tell police and dependable neighbors when you plan to be away and ask them to keep a close watch on what's happening in your area.