Keep it simple. Not every action on screen needs to have a sound effect.
Add sound effects for mouse clicks and typing.
Don’t use bubbly and excessively cartoonish sound effects.
Don’t be afraid to remix and rearrange your tracks.
Look for ways to create contrast. For example, stop the music and bring it back at a different point in the song.
Try to get the music to work with the voices and not simply play in the background.
Be careful not to let your music get repetitive. Avoid letting a single track run through the whole video.