Two other things that I think worth mentioning:

1. You want to see an active community discussing that particular ICO - if you don't see people actively debating the strengths and weaknesses and how they can be solved, then it's probably not going to catch on...

2. I was always a little suspicious of ICOs that offer a bonus structure, and this is something that Vitalik Buterin also recently mentioned in one of his tweets. If they have to offer you a bonus to buy into their ICO early, then they're all about the hype rather than the actual product content. It could also mean that they don't believe in the product themselves and it won't survive in the long-term.