My first step is looking rating when I search about ICO. It doesnt mean I totally trust it but it gives a route.
I am initially also looking for ratings when I search for ICO. but first I check first because I fear if there is fraud in it. so research is very important. I think ratings are not for our guaranteed success or we are told to trust them. Because I think they can also be bought by anyone. So you should be wary of the words of the rankings.