Making sure they dont give you promises of profit (things like regal coin and bitconnect are good to flip but they aren't real businesses)
Companies with real sponsors of big companies that have done their due diligence
Companies with a working product
Companies with a good team / advisors
To avoid ICO scam is always be vigilant and follow your instinct. It is not 100% guarantee that you will avoid scam but atleast you make your own effort to prevent it to happen. And the important to do is to make a research about the ICO and developer/manager handle the project. And dont easily trust if someone promise you a big amount of profit right away.