I look at a few different aspects in a ICO when looking to invest.

If I were to break it down to the top 3 most important I would have to say the CEO/team, the community it has and behind it and finally how the tokens will be actually used in the product they are trying to bring to the table. I have seen a lot of revolutionary ideas in ICO's starting to come out in the scene but a lot less have actual case uses for the actual token you be purchasing. Besides that a very active strong community is a great thing to see and a good indicator of future success.