Most of the ICO's are shit.
The best way to know that an ICO is legit, is seeing that the team already has a working product (for example, BitDice has a running casino for 3 years, and now they come with an ICO).
And, what Whipsplash says: the more info you can find beside their webpage, the less likely it is that is is a scam.
I agree that the team is important. If there is a famous casino or some known people working on the project (which I guess is a rare thing) then it is not a scam. Yet even this doesn't guarantee the project's success, so investing in icos is really hard and risky.
How to spot scam coin? You need to do some research on their whitepaper and development teams and I find it difficult to determine the scam coin just by those two factor but it will surely narrow it down a bit.
I suppose the question here is rather how to find a non-scam coin that the opposite. By the way, maybe all these Chinese regulations will help to deal with this matter, for I saw the news about the ban of suspicious icos, not all of them.