You should buy when there is real panic on the market and you should watch out for some strong support lines in a 1D chart, to grab it at good a point. I dont prefer to grab hyped coins, because the most are going to correction in the most cases
Always grab the opportunity to buy when their is panic that resulted into price is cheap. Also, it is good to buy when the coins has its potential to grow. And yes I agree, dont buy those hype coins because mostly when you dont know to ride with the train somehow you will lose.