Chip Camden asserts that you don't need to be perfect to build trust with clients, but you should be genuine with them.
As a consultant, you take great care to protect yourself. You should have a contract to legally bind your transactions with your clients. You establish policies and procedures to set expectations and minimize risk. You buy insurance just in case everything heads south and you get sued. Those all comprise a safety net. While it's good to have a safety net, nobody wants to go back a second time to see the acrobat who fell in one. Likewise, if you resort to defending yourself against your client, you've already lost any productive relationship with them.
To keep flying high with your client, you must develop a relationship of mutual trust. The acrobat can avoid landing in the net after a triple flip off the flying trapeze only because she knows that when she completes her last turn, her partner's hands will be waiting for hers. If you want your client to come back to you again and again, they must be able to trust that when they reach out to you, you'll catch them.
How do you build that degree of trust? Obviously, you must come through for them time after time. Keep your word. If you find that you can't meet a commitment, admit it early rather than later and work with your client to find a way to salvage the situation.
But there's more involved in trust than just your track record. We humans aren't strictly rational animals. Part of us operates at a pre-rational level -- we often make decisions based on a "gut feeling" and then employ our rational facility to justify those feelings. Humans have relied upon trust and mistrust for a very long time, long before we developed systems of rational analysis. It's something we smell, metaphorically and perhaps to some degree literally.
One of the smells that tips off the need to reserve trust is when we sense that the other person isn't being genuine. It may be about something that has little to do with their ability or willingness to execute on our mutual agreement. Nevertheless, it may stifle cooperation. For instance, if a consultant presents himself as a know-it-all, the client's caution flags immediately go up. The consultant may indeed possess far greater knowledge of the problem domain, and strictly speaking it might be more efficient to ignore the client's uninformed hypotheses 99% of the time. However, the client will perceive this haughtiness to be an attempt to project a "better than thou" image, and will instinctively see that as false.
We've all been tempted to exaggerate when retelling our own experiences (and if you say you never have, you're exaggerating). Even though it can make a story more interesting, your auditors can often sense when you begin to depart from the truth. They might forgive a harmless embellishment here and there, but to the same degree they'll have to wonder just how true to life your status reports and invoices are. That mistrust may not even reach a conscious level -- in which case it is all the more dangerous.
The best course that I have found is to keep it real. The image you project is not anywhere near as important as being yourself. I'm not saying that I've arrived by any means, but I've learned to detest that feeling that starts somewhere in my stomach when I'm thinking one thing and saying something else, or smiling only on the outside. Not only does brutal honesty prevent that dishonest smell, it requires less energy devoted to remembering what you said to whom.
We often find this kind of genuineness difficult because we're afraid of ourselves. We base the image we project to others on a concept of ourselves in which we wish to believe, and sometimes we actively engage in convincing ourselves of its truth. That has to go. We have to accept ourselves for who we are, and recognize that every person no matter how great they were had their own failings. Once we've done that and made peace with our limitations, then we can allow ourselves to be imperfect in the eyes of our clients. Believe it or not, clients don't want you to be perfect. Clients want a real human being in whom they can trust.Also read: Resist the temptation to do wrong by your clients