Be aware of your surroundings. If you're recording with a "track" rather than a live pianist, try to select a room that has well-balanced acoustics. You want to refrain from spaces that may be too resonant or echoey, where the clarity of your diction gets lost or may become unclear. Check the balance between you and your accompanist.
Make sure that no background noise (like dogs barking, running dishwasher, ringing phone, sibblings,etc.) will interfere with your recording or interrupt your performance.
Make sure the space is well-lit. We need to see you clearly.
If possible, use a tripod or stand for your video recording device on a table to help stabilize the image being recorded, rather than relying on someone's hand to hold it and keep it steady.
Test the view of your camera, ensuring that your whole body is in the frame, but keep the camera close enough that we can see your facial expressions. Judges will be evaluating beauty of voice, technical skill, musicality, accuracy, communication of text, diction, and presentation. Pianists, we need to see your hands and feet as well as your face and posture. Instrumentalists, aim to include your whole body as well as all of your instrument. (bow arms)
If you are using a recorded "track" rather than a live pianist for accompaniment, make sure that the sound level of the track is balanced to the level of your voice.
Do a "test run" through several phrases and then listen back to ensure you are in the frame and that the sound is not being distorted in any way.
Perform your piece straight through, from beginning to end without stopping. No mixing, voice amplification, sound enhancement, audio dubbing, or splicing of multiple "takes" together is allowed.
Record each song in a separate video file.
Record your introduction separately as well.
A placard held up at the beginning of the video is useful to introduce your songs. Make sure it is legible and dark enough print on the recording.