1. Choose the right weather and time. It is best to harvest in sunny morning or evening, and avoid harvesting in rainy days or in the hot sun at noon, because the fruit will affect storage, transportation and sales after being stained with mud.

2. Find the ripe watermelon. Maturity can be judged by observing the appearance characteristics of watermelon, such as observing the color of watermelon skin, whether there are yellow spots, whether the sound of knocking on watermelon is dull, etc.

3. Use appropriate tools. You can pick watermelons with a knife or scissors, and avoid pulling or twisting watermelons directly by hand to avoid damaging vines.

4. Pay attention to handling when picking. When picking watermelons, put them down gently to avoid being broken or bumped.

Pay attention to the following points when selecting watermelons:

1. Avoid picking immature watermelons. Immature watermelon has low sugar content and is not sweet enough.

2. Avoid picking more than 70% watermelons. More than 70% watermelons are easy to crack, so leave a section of stems and leaves to avoid cracking due to excessive maturity.

3. Avoid picking watermelons with wounds. If there is a wound on the surface of watermelon, you should avoid picking it, because the wound is easy to cause rot.

4. Avoid picking watermelons that are too heavy. If the weight of watermelon exceeds the normal range, you should avoid picking it, because it may be an overripe watermelon or a watermelon with pests and diseases.

5. Avoid picking watermelons with defective appearance. If there are scratches or other defects on the surface of watermelon, you should avoid picking it, because this may affect the quality and storage time of watermelon.

In short, when selecting watermelons, we should pay attention to handling them gently to avoid damaging watermelons and affecting their quality. At the same time, we should choose the appropriate harvesting time according to the weather and time, and pay attention to judge the maturity and quality of watermelon to ensure the high quality, good taste and storage resistance of the harvested watermelon.