When lifting anything, regardless of the weight, be sure to keep the object as close to your body as possible. The further the object is from your body, the more likely you are to injure your back. Also, bend your knees and lift with your legs, not just your back.
One other thing to avoid is twisting while bending. The low back is very vulnerable to injury when it’s rotated and bent forward, so please do only one motion at a time.
Remember, prevention is easier than surgery or months of therapy!