Summarize this article:

If all other factors are equal, it's hard to hurt the quality of a trailer by ditching low-quality equipment for top-of the line hardware. Trailers that are shot with crystal-clear, high-quality cameras and microphones and put together with professional-grade editing software will have a much easier time looking and sounding amazing than those shot on a shoestring budget with inferior equipment. While it's certainly possible to create beautiful, effective trailers while working around these types of budget and equipment limitations, this requires extra work and planning. Note that trailers are usually (but not always) pieced together from footage from the movie, not shot on their own. Thus, to be clear, it's often best to shoot the movie itself with this high-end equipment, rather than reserve this equipment for the trailer alone. Planning is absolutely crucial for making a gripping trailer. Even if you're making your trailer entirely from preexisting footage you shot for your movie, it's still very wise to have a shot-for-shot plan before you step into the metaphorical editing room. If you don't have a plan, you may find that your time is wasted: with a feature-length movie's worth of footage to work with and no roadmap to follow, it can be extremely difficult to even get started.  This being said, it's important not to devote yourself too heavily to your storyboard. In the world of cinema, plans are meant to be adjusted on the fly occasionally. You may, for instance, find that certain clips that you thought would play perfectly just don't "work" in the greater context of the trailer — in this case, be prepared to adjust your plan to correct these errors and make your trailer as good as possible. Never created a storyboard before? See our storyboarding article to get started. ) Good trailers have a natural "rhythm" that's almost impossible to describe adequately. The images and sounds in the trailer seem to "flow" into each other in a logical yet effortless way. Each clip is the perfect length — not so short that it's hard to tell what's going on, but not so long as to be boring or distracting. This requires precise editing and a good "feel" for the visual language of film, so if you're not an experienced editor, work with one as you piece the footage for your trailer together. Because of the time and energy required to carefully edit a movie trailer together, many studios now hire third party companies to do some or all of the work of creating the trailer. If you have the money, consider contacting one of these firms (or an experienced freelancer) about helping you with your trailer. You may find that you even saver money in the long run by reducing the development time of the trailer. Sound (and especially music) can be a big part of what makes a trailer effective. The best trailers use  sound and music to magnify the impact of the action on screen and establish the mood of the trailer (thus hinting at the mood of the movie itself.) On the other hand, bad trailers may use sound and music in a way that doesn't complement the action or may make the music the focus of the trailer, rather than the action itself, distracting from the trailer's message. One example of a great use of sound and music in a movie trailer is in the third official trailer for Nicolas Winding Refn's 2013 crime drama Only God Forgives. While the movie itself was met with middling-to-negative reviews, the trailer is truly memorable. The trailer opens with images of confrontations between criminals, complete with implied violence. These shots are accompanied by a 1980s-inspired, driving, arpeggiated synth line that perfectly fits the retro, neon-drenched aesthetic while conveying a sickening sense of dread. Later, the sound cuts out during slow-motion footage of a gang shooting except for the twinkling, almost childlike keyboard melody of a ballad by Thai indie band P.R.O.U.D. for a truly chilling effect. Not every trailer relies solely on footage from the film to relay the basics of plot, setting, characters, and so on — some take a more direct approach by including voiceover narration or text cards to help give context to the footage onscreen. However, this option must be considered carefully — if overused, voiceovers and text cards can distract from the footage itself and lend the trailer a cheap or run-of-the-mill feel. When in doubt, abide by the common sense rule that, in art, it's usually better to show than to tell. One trailer that uses voiceover work in a restrained way that compliments the trailer itself is the trailer for Paul Thomas Anderson's 2014 adaptation of Thomas Pynchon's Inherent Vice. In the trailer, a coy female voice relays the basic plot of the film in a humorous, deliberately campy fashion that fits the early 70s California setting and the comedic tone of the film. The narration appears only at the beginning and end of the trailer and never distracts from the action. The narrator sleepily delivers sarcastic lines like "Doc [the main character, a "slacker" detective] may not be a do-gooder, but he's done good ... good luck, Doc!" and ends the trailer with the self-aware "Coming just in time for Christmas." As a general rule, trailers should be no more than a minute or two long. Typically, full-length trailers run about two and a half minutes, though this is not a "hard and fast rule." In fact, the National Association of Theater Owners has recently spearheaded an effort to restrict trailers to a strict two-minute runtime. Regardless of the content of your film, try to squeeze all the important beats in the section above into a short, tidy package. Remember — the longer your trailer, the more of a chance your audience will have to get bored with it. Trailers longer than three minutes are very few and far between. One semi-recent example of this type of long-form trailer is the nearly six-minute "Extended" trailer for the Wachoski sibling's 2012 adaptation of David Mitchell's novel Cloud Atlas. Though the longer format does lend itself to the film's complex narrative, which is woven between six different settings and time periods, the creators wisely chose to also release a standard-length version.

Summary:
Use the best equipment possible. Storyboard or draw out your trailer. Keep your editing snappy (or find someone who can do it for you. Choose music and sounds that fit the mood of the trailer. Consider adding voiceover or text cards. Refine your trailer to about two and a half minutes of footage or less.