Just buy it when it falls. For example, the current price of sugar is 7300. If you think its price is too high now and may fall, open a position to sell sugar at 7300. If sugar really falls, you will make money. For example, if the price drops to 7240 and you open a short position at 7300, you will make a profit of 60 in one hand.

I am from a futures company, you can chat with me in detail