The Problem with buying and holding is to hope the project is solid and devs are really active on their part if not then you are in a top situation. I will recommend you research and watch the project attentively, know when to sell and when to buy
In order to find a solid project and good coin, an extensive research is needed.
Many coins are available in the market but only few of them are worthy. Choose what you think is profitable and has potential even you hold it for long period. As always just only invest the money you can afford to lose.