#1 Poor Camera Work - Someone who has shaky hands, can’t pull focus or lacks knowledge on how to frame a shot will kill your video before you've even started an edit.
#2 Poor Planning - Smashing a bunch of shots together, without a good story or message screams poor planning. Make sure your message or script is tight before you shoot.
#3 Bad Audio - Wind, background noise, abrupt starts and stops, poor mixing… it all counts.
#4 Bad Lighting - Harsh shadows and contrast, overexposed backgrounds or lack of details from darkness will kill a shot, and make it unwatchable.
#5 Poor Graphics/Transitions - Keep your graphics and transitions simple and clean or they will be distracting, don’t cheese up your video like an 80’s car commercial. Notice highly produced video and commercials don’t use them, there’s a reason.