You’ve worked hard to get a foot in the door with a choice client. Now, how do you get your other foot over the threshold? With internal referrals.

As a small business owner, you’re no stranger to hard work. You’ve built your business from the ground up, and you have likely spent countless hours and thousands of dollars marketing yourself and your company. Sometimes, though, the best way to find a new client is to work within the customer base you already have.

Once you have solved one problem for one client at a large organization, you can grow your business by winning new clients in other departments. Internal referrals carry significant authority because you have already proven that you understand the culture and priorities of the client company. If you did it for one department, you can do it for another.

The secret to winning internal referrals is to help build your client’s career. While your client may look like a hero for bringing you in to solve a problem, he or she will look even better for sharing you. That builds your client’s reputation as a visionary, and you are Exhibit A—someone who delivered long-term insight and not just a short-term patch.

Experienced consultants say that the best way to win internal referrals is to spend time investigating the cultural and political barriers that could keep even a straightforward recommendation from being adopted. Will someone be defensive, embarrassed, or protective about prior decisions? Will the solution you are likely to propose undermine someone’s credibility? Negate someone’s authority?

For example, a technology department head might resist your recommendation to buy a certain piece of software because it appears to undermine his prior decision to buy a difference piece of software.

When you have figured out these submerged barriers that could potentially get in your way, you can proactively build relationships with those staffers to win their support.

Seasoned consultants kick off a new project with a closed-door conversation with their key internal client in order to find out which internal influencers must be satisfied to get the job done. They then learn what has prevented others from solving this problem already.

Additional ways to deepen your relationship with your internal client include:

Providing informal feedback on your client’s performance that can help with professional growth. As an outsider, you have unique observations to share. When you do so in a positive way, you demonstrate that you are invested in your client’s success. Then, when your existing client recommends you to others within the company, that client feels that he or she is recommending an ally.

Adding value in unexpected ways. Pass on bits of research or news to your primary client that he or she can then forward to others within the company. Added bonus: Those others then get your direct contact information via your email signature and address.

Going out of your way to meet your client and his or her contacts at external meetings. As the client introduces you, he or she has a chance to tout your value to the company, reinforcing his or her role in finding the terrific resource that is you.

When you take some of your personal time to meet your client and that client’s contacts at industry and professional events, your client gets to know you in a different setting. When it’s time to recommend you internally, your new contacts have fresh and persuasive evidence of your credibility.

Collaboration with client contacts at all levels can help you smooth out friction in advance. This not only paves the way for success with your current project but also lets you demonstrate a deeper understanding of the company culture—and that makes you a real find for others in the company.

Joanne Cleaver doesn’t just write about entrepreneurship and finance for national publications and websites. As a longtime freelance writer and editorial project manager, she lives it. Her most recent book is The Career Lattice (McGraw Professional, 2012), which shows how lateral moves power career growth.