The most common practices that if you have doubt in a certain investment is just to invest only what you can afford to lose so that in case when the ICO goes wrong like a scam or a failure project then everything is fine then. If i'm very certain that its a good project then i invest the minimum order quantity but i will have the bonus token anyway.
honestly, right now I'm only monitoring the development of investments in the ICO. well, maybe there are some projects that are quite worthy of being invested based on investment time, concepts, and funds that have been collected. but that does not guarantee, because an ICO will not be trusted until the coins enter a market and have a reasonable price.