The best way to prevent "double charging" a shell casing is to weigh each one using a powder weighing scale. A strong light and your Mark I eyeball are also usually adequate to the task. I haven't reloaded pistol or rifle ammunition since sometime in the previous century, but it sure makes sense if you want to practice a lot, or just want to "tune" your cartridge to match the capability of your weapon.
Keep sources of static electricity, sparks, and open ignition sources far away from your reloading bench. Same goes for distractions such a pets, curious children, and visitors: keep them away while you are actively engaged in a hobby that can kill or seriously injure you or bystanders if something goes wrong.
