FORTUNE — You show up to a professional engagement, maybe a networking event or drinks with a former colleague. You expect to talk about your career trajectory or the other person’s. You’re there to build your network, to foster professional relationships outside of your office, maybe even to talk your way into consideration for a job you’ve been eyeing. But when you sit down, the conversation steers away from your work interests and heads into personal territory.
That’s when it hits you: You’re not enjoying a networking cocktail. You’re on a date.
In a business world where almost 40% of the workforce reports having dated a coworker, the lines between professional socializing and dating are blurry. But while many offices have clear, written policies about this kind of behavior, there are no such rules when it comes to networking. This no-man’s-land has turned into a minefield for single women trying to hustle their way up the corporate ladder. The waters are murky for men too, but as Ivan Misner, author of Business Networking and Sex: Not What You Think, notes, women encounter these situations “far more than men.”
MORE: 5 toughest work conversations
If you don’t want to find yourself on a date, make sure that that isn’t what you’re arranging. This begins with the initial invitation. Twanna A. Hines, an educator, writer and commentator who focuses on the relationship between sexuality and culture, advises networkers, “Be clear from the beginning what your intended outcome is for the meeting.” The more specific, the better. “So when you’re setting it up, express those outcomes.”
The logistics of the meeting matter too. Dorie Clark, a personal branding expert and author of Reinventing You: Define Your Brand, Imagine Your Future, advises keeping professional networking to daytime hours, where there’s less room for misinterpretation. But, she admits, this isn’t always possible. Some people are simply too busy during standard 9-5 hours. In those cases, Clark says to make sure your attire is professional. “Even if you’re meeting someone for dinner or drinks, don’t dress like you’re going out dancing,” she says. And, just to be safe, she advises, “Always have a plan of somewhere that you’re planning to go afterwards.”
But even the best-laid plans sometimes go awry. If, despite your efforts, you find yourself on an accidental date, all is not professionally lost. “Your top goal in this situation is to try to ensure that the conversation doesn’t progress to the point of no return, meaning the person making an explicit pass at you,” Clark says. If the conversation seems to be veering in the wrong direction, try to bring it back to professional topics, or casually mention your significant other. (Don’t have one? According to Misner’s research, it is not uncommon for unmarried women to wear wedding bands to deter men from hitting on them in professional environments.) Clark and Misner both suggest bringing another colleague along to meetings to defuse unwelcome romantic tension.
What if you’ve done everything you can to let the other person know your interests are professional and not romantic, but you still sense the person is looking for more? Can you still accept their help? According to Clark, “This is where your gut instinct comes into play.”
If the person is a lost cause, walk away. But, “As long as you think that the person has good intentions rather than malicious ones,” Clark says, “I don’t see a problem with trying to do your best with integrity, to receive their professional help, and to give your professional help to that person.”
Hines offers similar advice, “If someone offers to help you and their motivation for doing so is that they were hoping to sleep with you, that doesn’t in any way obligate you to sleep with them or feel guilty if you don’t.”
MORE: Spotting the hogwash in business advice books
Misner recommends exercising caution in such scenarios. Be sure you are not flirting with the person or using your sexuality to interact. “It’s not very authentic,” he says. “And if you really want to build business relationships with people, you need to be authentic.”
He also offers advice to the person on the other end of the conversation. After all, sometimes a romantic advance will be welcome; the key is identifying the difference. To do that, you need to build a relationship. “Men have a tendency to cold call,” often forgetting to lay the groundwork, Misner says.
Instead of hitting on a colleague right off the bat, get to know the person. “When you’ve established a relationship, then taking it to the next step may be more obvious for you,” he says. He would know — he met his wife at a Leadership Training held by his networking organization, BNI.