They are great ways to get into coins early on before they hit the exchanges. A lot of the time, the companies will give bonuses for being a early adopter. When deciding on which ICOs to get into, I like to look at the whitepaper, the team, ICO structure, the community support on Slack, Telegram, and Reddit. If you can get into a Pre-ICO that is even better but many require minimum investments. Some Pre-ICOs that I recently got into were Enjin (Ends in a few days), AirToken, Kyber, and OMG.
I have been investing in ICO's for the past year or so, and I have a similar strategy when deciding which ones to pick. Both Enjin and Airtoken have potential. I don't know much about Kyber, and OMG has been trending upward for the past month.