USE HD CAMERA; Many smartphones has the option to turn on the HD camera. ALWAYS record the videos using this feature and don't forget to use the smartphone recording Horizontal .
RECORD SMALL VIDEOS; you will do a short video with the best memories of your event, day or moment. So try to record small clips (15-30 seconds) at the end the final video to share in social media will be better in 1-2 min.
DOWNLOAD AN APP: there are many good and FREE apps to edit a video in your smartphone. I love CLIPS, iMovie, SPLICE & VIDEOSHOP. These apps have great Transitions, let you set up the time between each image or clip, and have a lot of copyrighted music!!!
For a better explanation feel free to watch the next Small Video.