How to take useful photos for plumbing and electrical rough-in documentation?

When taking photos for plumbing and electrical rough-in documentation, many people just snap a few random shots, but they end up being useless when it comes time to drill holes, install cabinets, or open access panels later. Without reference points in the photos, you can't tell how far the pipes are from the wall or floor, or even which wall it is. Once the drywall is up, if the owner wants to…