We understand your curiosity. You want to be prepared when the moment arrives. But it's probably better to wait until your first (or even second) period arrives. Why? Because the menstrual flow moistens the vagina and helps the tampon slip into place. Waiting a bit also is good because it gives you a chance to get an idea of what your flow will be like — heavy, light, or somewhere in between. When you know your flow, you can pick the right tampon for your needs. For first-timers, try a slim fit-sized tampon, then relax and read the instructions.