It is very important that before entering a trade, you should first have a plan for that certain action that you'll be doing. For example, have an entry and exit price for that coin. After that, do your own research about the coin that you'll be trading. I usually base my trading period on the amount information that I got for that certain coin. If it has a good technology backing it up, I usually hold it for 1 to 6 months. If I found out that it is an interesting project but don't have good devs backing it up, I usually trade it in short-term period, 1 day to 1 week.