I think the best and most effective place to advertise an ico is the bitcointalk forum, signature campaigns or crypto related forum because mostly the members of those forums are crypto related and will likely drive a traffic and investments to your sites and ico rather than using the social media platforms.
it is true this forum is still the best because it is the users ICO is looking for information here and the development of ICO is here so no doubt this forum is still the best to be a marketing medium.