Trick #1 - Let there be light.

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Not having enough light is often the main give-away that marks a video out as "Amateur". You can not have enough light when making your video. Without it your videos will look dark and grainy, often in extreme cases the subjects can only be detected as silhouettes! - So get some light on your subject.

If you can afford a professional lighting system, then go for it - you will always get consistent quality results.  If not - Improvise! Simple clamp-on lamps, cheap work-lights, or even ordinary table-lamps with their shades removed will all do the trick - Just make sure there is enough light to make your subject look well-lit in your video monitor. If it looks good in your monitor, it should look good in the edit.

NEXT >  #2 - Use natural light