Every celebrity is an entrepreneur, and like most entrepreneurs, some are better than others. It’s up to celebrities to find ways to promote themselves and their personal brand.

So, in between acting and singing gigs, the Olsen twins, Jessica Simpson, and Gwen Stefani have carved out secondary careers in the apparel business. These celebrities found opportunities to build further success with their own companies, but the stars are always looking for partnerships, and those partnerships can be bartered, borrowed, and sold.

If you’re considering celebrity marketing, you already know that a celebrity endorsement can increase sales and build excitement for your brand. One of the first questions a retailer and prospective client asks is “Which celebrities are using your product?”

If your business doesn’t have the funds to advertise, then you need to take into account celebrity marketing. Retailers that carry your merchandise, or those that are considering carrying your merchandise, will welcome your celebrity-marketing efforts because they help drive sales to their stores.

If you are still on the fence about celebrity marketing, consider the insatiable appetite that the American public has for anything celebrity related. People magazine has long been a place to catch up on celebrity gossip, but it caught the fashion world’s attention when readership started climbing to over 3 million (as of the first half of 2011, it’s up to 3.5 million). So did US Weekly, which came in second at almost 2 million.

Vogue’s editor in chief Anna Wintour has increasingly been putting celebrities on the cover, recognizing that celebs sold magazines, along with the merchandise they wear to events and in their personal life. “The bottom line is celebrities sell much better,” Wintour told one writer.

Over 30 percent of the 2,400 U.S. magazine pages feature celebrities.Some celebrity-driven websites reach almost 4 million unique visitors, so consumers are one click away from a sale.

Still not convinced celebrity marketing is “right” for your brand? Let’s take a look at an example from a celebrity’s point of view. One day I got a phone call from Gene Simmons, the bassist in the band Kiss. He wanted to talk about launching his clothing line. Although it wasn’t the right product for my company, I told him how smart he had been for building his brand through numerous commercial avenues—all independent of the band. This is an example of a celebrity who has used his fame as a launchpad for business success. Gene offered me a testimonial I’ll never forget: “If the train is leaving the station, I might as well fill the seats.”

Although Gene may not be the right partner for your brand either, the rocker is exactly the kind of celebrity I look for when I am consulting with a company looking for a celebrity partner. You need a celebrity with built-in media interest, a star with interest in your product.

Ralph Waldo Emerson penned the famous words, “Hitch your wagon to a star” about 150 years ago, and the saying still holds true when it comes to working with celebrities. I built my business on this idea and helped many clients benefit by “hitching their product” to a celebrity.

Where to start? Some research is key. If you are considering celebrity marketing, start checking out magazines like People to familiarize yourself with the hot names their readers want to know more about. Pick up any celebrity weekly magazine and you’ll see photos of Taylor Swift, Joe Jonas, Justin Bieber, Demi Lovato, and Selena Gomez. Teen stars change frequently, with a whole new crop waiting for their shot. So, if your product appeals to the teen market, it’s important to figure out which stars teens are following. Appealing to the Y and Z generation (those born in the late 1990s) can be very lucrative.

Finally, here are a few deciding factors to consider before jumping into the waters of celebrity marketing:

• Get your sea legs first by building your business, and then consider working with Hollywood stars.
• Expenses can add up—make sure you’ve added realistic costs plus surprise costs into the equation. Remember, rarely do you get something for nothing, and this is especially true in Hollywood.
• Where is your product sold? Have an e-commerce website or, at least, one store where consumers can purchase it immediately.
• Be prepared to beef up production of your goods to handle a jump in sales if needed.
• Bartering product is cheaper than paying for an advertisement or endorsement. If a celebrity likes your product, be generous.

The bottom line is that celebrities are real people, in spite of the mega-salaries they command and the lifestyles they lead. Like real people, they are complimented to receive something for free or to have the chance to borrow something, instead of buy it. After all, who wouldn’t like a closet you can dip into when you need something?