I prefer cheap coins from the top 50. I'm sure that the maximum profit can be obtained from young prospective ICO. But unfortunately it's difficult for me to see the potential, so I choose already declared themselves crypto-currencies.
make sure before investing you research first altcoin that will be made in place of investment. if I prefer to invest in ETH because ETH is no doubt the price is always good and popular so I stay buy when the price drops and keep in the wallet until now.