Napoleon had Waterloo. Lee had Gettysburg. Custer had the Little Bighorn.

After his blunder, Napoleon was sent into exile. After Gettysburg, Lee never again invaded the North. And after the Little Bighorn--well, there was no "after" for the reckless Custer.

Entrepreneurs are far luckier than generals. For one thing, we seldom put our lives on the line. For another, though most of us have failed miserably at one point or another in our careers, the best of us have learned valuable lessons and become better leaders as a result.

So here I recount the three biggest new-business blunders in my career--and impart the useful, if painful, knowledge I gained as a result.

1. Underestimating a new business lead

We were once approached by a company that made specially equipped vans for handicapped people. When they asked if we would be interested in representing them, we said sure, but we treated the opportunity far too lightly. In fact, we didn't even rehearse until about an hour before the presentation was scheduled to begin.

Our team decided not to present in person. Needless to say, our competitors took the new business lead very seriously and sent their full team to meet the prospect.

It gets worse. I showed a photograph of a handicapped-accessible van parked outside a retirement village. I began my explanation, but the prospect interrupted me. "Steve," he asked, "you do know the slide you're showing contains a photograph of our No. 1 competitor's product, correct?"

When my heart began beating again, I opted for humor. "Of course," I chuckled. "We just wanted to make sure you were still paying attention to the presentation."

The prospect wasn't amused. Needless to say, we received a "Dear agency" letter the next day informing us the business went to our competitor.

Lessons learned: Never pitch a piece of business unless you're willing to invest the maximum time and resources necessary to win it. And never wait until the last minute to rehearse or review the contents. We now work backward from a presentation date and rehearse multiple times.

2. Trusting a mole

I received a call once from a good friend who also happened to be the in-house general counsel of a global international consulting firm. "Steve," he said, "not only are we firing our PR firm, but I know exactly what they did wrong and I know exactly what the CEO and COO want from the new firm."

We were thrilled to compete and ended up sharing every strategy and tactic with my friend, who massaged them at every step. I don't think I'd ever felt more confident striding into a prospect's conference room than I did walking into the consulting firm's that day. When the presentation ended, the CEO was the first to speak:

"That had to rank as the most glib and superficial presentation I've ever heard," he said.

The COO applied the coup de grâce: "Steve, why did you just assume this is what we wanted?"

We did our best to regroup, but we were dead in the water. Steaming, I ran to the nearest phone and called my friend. When I reported the results, he replied, "Hmm. I guess things must have changed between then and now." That was it. My best guess is that he had overheard snippets of different conversations and leaped to the wrong conclusions, but I never got further explanation.

Lessons learned: Don't trust an inside source at a prospective client's organization. Always depend on what the lead decision maker tells you in her brief.

3. Drinking your own Kool-Aid

Like many firms in my field, we've dramatically changed the range of services we provide. So though we began as a traditional public relations firm 19 years ago, we have subsequently morphed into a fully integrated strategic communications firm.

In our early, PR-only days, we had the good fortune to represent a top office-products manufacturer. But as is often the case, the old management team that had hired us was swept out and replaced with a new one. And when a new sheriff arrives in town, the first person he shoots is the existing PR firm.

Fast-forward five years. One of the original clients had returned to the office-products company, in a much more senior position. Now that he was the sheriff, he was anxious to shoot the existing firm and bring in his favorite (that would be us). And so he arranged a capabilities presentation to his fellow managers that we assumed would be little more than a rubber stamp for him to hire us.

But there was one slight twist. "Joe" asked that we update him on the "new" Peppercomm. Rather than review our still-considerable public relations capabilities, we instead launched into a 40-minute review of our amazing new array of sophisticated client service offerings. The managers didn't seem impressed in the least. At last, Joe stopped us and said, "Hey, Steve, we're looking for a PR firm. It seems to me that Peppercomm doesn't even do PR anymore. But thanks for the update. We'll be in touch."

We were dead. I tried my best improvisation routines to win them back, but we had blown a golden opportunity. The PR account went to another firm that, you guessed it, did nothing but PR.

Lessons learned: You don't want to begin a meeting by extolling your firm's virtues. Instead, ask the prospective client to restate the exact scope of the assignment for which it requires assistance. Had we only asked, we would now once again be working with Joe.

The great thing about business (as opposed to war) is that leaders can live to fight another day. And, trust me, I now go into battle a chastened, if better prepared, leader. I may have been humbled by three horrific blunders, but each has made me a better entrepreneur and my business a more formidable competitor.