I strongly advise you to hodl. New research (
https://onegram.org/hodl-day-trading) shows that hodlers make the same amount of money as day traders, be it with less action. To choose what currency to hodl or trade you have to review their whitepapers. Make sure to research your potential trading candidates thoroughly. After you understand each currency's underlying technology and the development team's roadmap, either analyze potential gains as in usefulness for industries or simply trust your gut. You could also read what crypto investors have to say about the candidates and trust their predictions.