A lot of beginner-friendly chords like E, Em, A, and Am, for example, really need a lot of room for the strings to ring out. If you ever find yourself playing one of these chords and the string(s) keeps buzzing, or muting on you, try pretending that you are holding a ball in your hand.
This will allow you to keep your fingers, and hand, curved and in a nice round shape that allows the strings to pass through your fingers, without them falling or touching the other strings, causing them to mute out.