Report them to the authorities, use social media to post warnings about the ICO and don't forget to provide concrete evidences to support your claims or create a website for posting the list of ICO's that are considered scams.
Won't work, scams are always vanish right after they been detected at scamming. Vanishing with all of your money by the way
The best advice is to do your own research. Scammers will never quit. The best advice is to call out the scams as soon as possible to limit the number of suckers they can hook.