I think the good point of reference to exclude scam ICO is how long people have worked on the project before launching the ICO. If it's only few months or weeks there is very high chance that this ICO is a scam. The real projects take quite a lot of time to plan, to prepare meaningful white paper, and finally to launch ICO. The professional field background of the ICO team in the field that the ICO tries to address is quite significant. I think that it can be seen when the project "idea" was born just "yesterday" and is already on ICO. Common logic is good tool in this case.