Adhere to the basics.
Get a tripod and some lights. These things are pretty basic but make a huge difference and set a tone for the Vine. The bulk of the content created in this app is grainy, dark, jittery video made by shaky-handed tweens so it really stands out to increase the production value with a tripod and a lot of light. Even just a little clamp from a hardware store to steady the phone on something and turning all the room lights on makes a huge difference. The colors are better, the action is smoother and it's more watchable without a jarring cut at the looping point.
Vine: "WELCOME TO THE MANCAVE - NOW GET THE FUCK OUT" was shot in my living room on a tripod. I created a music loop and cued the action, fog machine, and disco lights to all go on at the appropriate time.