It's not rocket science... Players that are considering your game are going to be looking really hard at that trailer to make their decision. You gotta have a good video.
Hyper Light Drifter looks amazing on video.
Icon, Screenshots, and Video are the most important factors deciding whether or not a new player downloads your game. So do a good job with this part!
Examples of Cool Game Trailers
Now if your game naturally looks great on video, you're already half the way there. If not, there are some things you can do.
TIP 1: Use the game's artwork. Take it out of the game and use it to tell a story or set the scene. You've already made all that great artwork, might as well get the most out of it!
TIP 2: Short cuts, changing angles. TV has conditioned us all to expect a new angle/shot/subject every 3 seconds. Long static shots of anything bore us quickly. Party Hard did a great job of showcasing its game using frequent cuts and simulated camera panning. If you need to show a long shot, zoom in and pan the "camera" slowly for a dramatic cinematic effect.
Alright that's all just a short post. If you're an indie dev and you've got your head buried in developing just keep in mind that proper Icon, Screenshots, and Video are not to be rushed. They are the #1 deciding factor whether a new user downloads your game.
Hope these tips help! If you'd like some more help with your game's trailer drop me a line.
About Me: My name is RySal #5 and I have a proven track record producing quality game trailers that go on to help launch successful games. You can find examples of my work in top grossing Featured spots on the App Store & Google Marketplace.