A great trailer is important for the success of your indie title. It will be the first thing potential customers see when they land on your Steam page. It's also a great tool to drive traffic to your Steam page before release, building up your wishlist before launch.
1. Avoid non-gameplay footage
Start by showing your core mechanic. Most people don't give your video more than 3 seconds so it's important to grab their attention as soon as possible.
2. Don't start with your logo
Unless you have produces a globally recognized title before, nobody cares what your company is, especially at the beginning of the video. If you have to, include it at the end.
3. End the video with a call to action
Those who watch the video all the way through the end are really into your game. End your trailer with a call to action, like a pledge to our Kickstarter, subscribe to our newsletter, buy the game on Steam, etc.
4. Capture footage with sound & NO music
Your trailer probably shows off a montage of the best looking footage from your game. Make sure to capture that gameplay footage with sound, but mute your music. Nobody wants to hear chopped excerpts from the soundtrack.
5. Export in 4K
Even if your footage is in 1080p. This will produce a lot of stretching, but it won't be visible on YouTube unless somebody watches it in 4K. The advantage of exporting in 4K is huge: your video won't get compressed as much and the sound will be in a better quality.
6. Keep it short
One minute is all you need for a teaser trailer. The launch trailer shouldn't be longer than 2 minutes. The longer the trailer, the fewer people will see your call to action.
7. Show variety
Show off contrasting scenes, things that show that your game has many surprises and a lot to offer.