The most popular kind of balloon vid by a significant margin is the blow to pop. Below that there's sitpops, pinpops, hugpops, nailpops, and stomping.
For a blow to pop, an increasing sense of nervousness and excitement as the balloon gets bigger and bigger is key. Most looners have these kinds of feelings when blowing up balloons, and they enjoy seeing those feelings expressed in a blow to pop vid. Another big thing is knowing how to neck a balloon really well (which means making the balloon's neck inflate and bulge out, making the balloon like lightbulb). Most poppers (and even a lot of nonpoppers) love a thoroughly necked balloon. Basically, the more the neck bulges out, the better. Finally, if the balloon happens to explode into a ton of pieces/shreds, showing that off is great. Many looners love seeing the shredded remains of a balloon after a blow to pop.
As for most of the other kinds of popping vids, a lot of them boil down to knowing the limits of a balloon and being able to tease right around the edges of those limits before crossing them and making it pop. For example, you can rub the side of a pin against a balloon and it won't pop so long as the pin's tip is never angled towards the balloon. You can use that trick to tease at popping the balloon a bit before actually doing it.
Also, when it comes to what type of balloons to use, 12 or 16 inch Unique brand balloons are pretty good. They're cheaper than other brands, and they have somewhat long necks (which makes the necking thing easier). The 16 inch Unique balloon is more or less considered the standard go to balloon for a lot of vids.