Batteries and memory cards. These are two essentials we as photographers need extras of. There is no worse feeling than being out on location to find that your camera or flash has run out of juice or you are out of memory. Sure, you can always carefully delete unwanted images to make more room on a crowded card, but that is a hassle and you might just miss the important shots while you are fumbling with your camera. If it's power you are lacking, well, there's no recovering from that. So the lesson here is to carry extra batteries and memory cards. Always. While having extras of these will save your tail in a pinch, it presents a problem on how to keep track of their usage. It does you no good to swap out a dead battery for another dead battery, or a full memory card for another full card. Here is a simple tip that I have learned along the way that can help you keep track of both batteries and memory cards. This is a top secret, professional tip. Are you ready? The answe...