Jaime Sparr, Senior UX Designer at Opendoor, lists a few ways you can improve your skills at giving good creative feedback about someone's product. The first is framing your feedback appropriately and asking open-ended questions that allow your teammates to respond without sounding defensive. Be clear about what you think could be improved by making suggestions, not demands. Also “cheerlead” early, and critique more thoroughly later.
When it comes to receiving feedback constructively, Sheila Heen‘s advice is essential in any field.