The criteria was essentially that it had to be in the top 100 for market cap, had to have incentive for HODLing the coin, be valued less than its competition and I considered what the coin could achieve in the future. In terms of research, since I invest/mine/stake for a living now I read as much new material on Crypto as I can, and I focus most of my attention on the top 100 market cap coins because low market cap coins can easily be manipulated (good for a quick buck but I value long term stability and growth over anything else).