It really depends from project to project... You always want to read over their whitepaper/road-map/etc, check out their dev team, and see their exposure in the media. Right now one of my favorite upcoming ICO's, they actually have a presale going on right now, is Lamden Tau. Great concept backed by a solid team team of developers who really know what they are doing. There has been news that they just signed a big marketing contract and I am just waiting to moon haha