First of all, the gourd should be ripe, and the thicker the wall, the better. The simple way is to shake the gourd. When shaking, you can listen to the sound made by the seeds inside. If the amplitude is larger, you should be able to hear the sound. If the wall is thicker, the crash will be more solid. There is also just below the navel, and the mature ones will be more concentrated and smaller. In addition, it is the shape. You also need to bring a vine, the so-called faucet. It is better to have a cross, which is complete.