For me the primary criteria is to look at the exchange and the market cap before investing in any coin. If I find any new coin on exchange like Binance, I study it throughly and then decide whether to invest in it or not. My decision involves two main factors. First is to see in which phase the coin is. Is it growing, matured, or in declining phase. I stay away from already established coins and try my hand at new coins. Second, I look at the market cap of the coin.