We must know the current market situation, we wait for the market price at the lowest point. Then we choose some potentially big coins, I suggest do not just focus on one coin only. This increases the chances of our profit, if one of our coins soar we can sell. Or maybe by holding it for a long time, chances are that our coins are higher. But do not forget to often update market conditions, because of rising and falling market prices are very volatile in a very short time.