Never go all out in just one currency. Bitcoin, ethereum, ethereum classic, litecoin, and monero are good coins to start with. Only invest what you can afford to lose. Resist the urge to convert your entire litecoin balance to ethereum if litecoin's value goes down (for example) because often times they'll bounce back up and you'll end up regretting being trigger happy. Be patient. Research the coins. If their concept sounds unique or otherwise promising, consider it for investing. For example, steem is a great concept that is going somewhere and is potentially a wise investment.