I look mainly few aspects:
1. The idea - is it real and achievable?
2. The team - do they have enough experience or no?
3. The whitepaper from the beginning till the end. It is given to be read. So read it!
4. The roadmap - when will the product be released ? If it is more than year, for me this is problem.
5. The product - is it the product interesting and will it be useful once it is done?

These are the main thing that I check in given ICO before I decide to invest/participate in bounty campaign.