Do your own research and try to exclude any possibility of an ICO being a scam. Try to find credible information.
And the best time to invest is when you can afford to lose all the money youre planing to throw at it. Because even when a project looks good, bad things can happen and the project can not go anywhere.
Were talking about huge profits here, and thats associated with the high risks involved. The minimum one can do is to reduce the number of risks by sourcing as much info as possible.