How do I buy upcoming ICO?

As a cryptocurrency enthusiast, I'm keen on exploring the potential of Initial Coin Offerings (ICOs). However, the process of purchasing upcoming ICOs remains somewhat elusive to me. Could you elaborate on the steps involved in purchasing an upcoming ICO? What platforms or exchanges should I consider? Are there any specific risks I should be aware of? Additionally, how do I determine the legitimacy and potential of an ICO project? Your insights would be invaluable in guiding me through this exciting yet potentially complex process.