The most important usually:
1. Famous Developers in Team
2. Interesting Idea
3.Apha version of project
This is the most reason why people invest on ICOs, there are some that includes the supply to be distributed in Bounty programs but these three is the most important. Though I am not looking this in an ICO but in a bounty campaign.
Most of us especially the investors always looking for alpha version of their project simply because we can see that the project can release the beta or the full version of their project. Its hard to know if the developer are famous but once you know that it is famous grab the opportunity to invest because the project will really success.