For a startup, producing a video advertisement is one of the boldest ways to announce your presence to a wide audience. In no more than a couple of minutes, a cleverly executed spot can explain what your business does and galvanize viewers in a way static ads can't.

YouTube clips can be produced and broadcast for lower cost than slick TV commercials, and don't need to conform to the same time restrictions. Connect with viewers in just the right way--by making them laugh, tugging at their heartstrings, or inciting them to action--and the video can generate instant brand awareness and many new customers.

The flip side, of course, is the potential embarrassment and damage to your brand you can cause with an ill-conceived ad. Striking the wrong chord can be devastating when the audience can easily voice its disapproval in YouTube's comments section and share the offending clip on social media.

For tips on how to avoid the pitfalls, I turned to Adam Lisagor, arguably the preeminent director of video ads for startups in Silicon Valley. His company, Sandwich Video, has produced about 140 videos for clients including Square, Flipboard, and Airbnb. His recent ad for Coin, a company that makes universal payment cards, has garnered nearly 8 million views on YouTube. Here's his advice on how to create a video that will represent the best side of your business, and potentially even become a viral sensation.

1. Length is flexible, but keep it brief.

Compared to commercials in other media, online video advertisements afford some freedom to tell the story of your business or product in greater depth. "Humans receive and retain information at a certain pace and in a certain linear order," Lisagor says. "So the longer Web format allows us the space to receive new information without having it shoved in our eyes and ears." He recommends keeping videos in the 90- to 120-second range; if the product is relatively straightforward, a minute or less can suffice. Be careful not to abuse the relative lack of time constraints, however, he warns. "If you have [viewers'] attention, don't squander it. It's the most valuable thing."

2. If you're not funny, don't make a jokey video.

Many videos go viral due to a smart, well-timed joke, so it's tempting to come up with a funny concept for your ad or at least try to inject some humor into it. That can be a smart strategy--or a disastrous one. "If funny comes natural to you as a storyteller, then tell a funny story," Lisagor advises. "If it doesn't, then forcing it is a huge mistake."

3. Use clear language.

As natural as your business's lingo is to you, viewers may be confused and turned off by it. "Marketing people often make the mistake of using industry jargon and buzzwords as shorthand for describing value," Lisagor says. One example he cites: "global solutions," a term businesses in all manner of industries say they provide to customers, without providing any specifics in plain English. Unpack acronyms in the video as well, he says, or they will all "jumble together into gobbledygook."

4. Make viewers envision using your product.

"If you can allow the viewer to project him or herself into a mental state of experiencing the product and having a positive reaction, it can go a long way toward convincing them that they should take the next step toward having it," Lisagor says. Not only does that take a careful match of images and language, it also requires you to admit the scope of your product's benefits. "If you try to make the response to a product seem more grand or have a larger impact than people intuit what it would, it'll have an adverse effect on your brand," Lisagor warns. "People don't like to be lied to."

5. Understand the limitations of what a video can do.

Just as a good movie requires a strong cast and a solid script, the effectiveness of a video ad ultimately rests on the quality of the product. "The biggest mistake to make when embarking on a video is to assume that a video can answer questions that the product can't on its own," Lisagor says. So try to produce as smart a video as you can, but don't expect it to succeed solely on high production values. If it doesn't blow up and get millions of shares, the problem may not just be the ad itself, but the business it's representing.