Ideally, you'll want to set the following ahead of your meetings:
Set a default camera
Set a default speakers and mic
(optional) Set join behaviors (mute microphone on join, auto-join audio, etc)
(optional) Set a virtual background
(Mac Users on Catalina) Permissions
Open up your Zoom app settings by clicking on the gear icon on the home section of the app. Alternatively, you can click on your account icon, then select "Settings" in the menu.
To set the default camera, click on Video. Then proceed to select your preferred camera. This is helpful if you have more than one camera or simply want to test your camera (confirm that you can see yourself with the camera selected).
To set the default mic microphone and speaker, click on Audio. This is helpful if you have speakers but need to use your camera mic or simply want to test your audio setup. There are also test buttons available.
(Optional) You can also set whether you'd like the Zoom to join by computer audio when you join a meeting or mute your mic when you join a meeting in this section.
NOTE: If you set the mute mic option, you'll need to actively unmute yourself after you join a meeting.
NOTE: Join audio by computer when joining a meeting will bypass the following prompt when you join a meeting:
(Optional) If you'd like to set a 'virtual background'. You can add other images or videos by clicking on the '+' icon.
(Mac Users on Catalina) If you are running Catalina OS, you will need to go into the "Security & and Privacy settings" (System Settings, Note: you MUST have Admin rights to do this, please contact IT if you don't.), and under the Privacy Tab allow "Screen Recording" for zoom.us, to be able to share your screen (even if the meeting is not being recorded).