I call this the Head & Shoulders rule: Most of the time in business you don't get a second chance to make a first impression. Yet this simple fact of life is by no means as obvious and well-understood as it should be. Since we're talking here about "real life," in which there are no second acts, rehearsals, or do-overs, it's critical to make sure that the first impression people have of you and your business is at least favorable--and, ideally, fabulous.

We're designed by nature to make lightning-fast decisions; it's an outgrowth of our earliest "fight or flight" instincts that were developed for self-preservation (to keep the animals we encountered from eating us). We make snap judgments hundreds of times a day. It's a visceral process, mainly subconscious, and it's far more accurate (in 99% of the cases) than many people, and especially behavioral "experts," like to admit. It turns out you can judge a book by its cover. Just not in the ways we used to think.

Bum or Billionaire?

In the old days, if you wore crappy old clothes when you went looking for a new car, the salesman would size you up in a flash and either ignore you or hand you over to the newest and youngest guy on the floor. Today, if you wear those same old duds to go car shopping (after, of course, you've checked everything out on the Internet), the salesman has to consider that you might be a major "in the money" code monkey or a mobile mega-millionaire--and has to treat everyone who walks into the dealership in the same fashion.

But while you no longer have to dress decently when you car shop, it's a different story in most other social or business contexts. There, the decisions you make in terms of your dress, your appearance, or any other aspect of how you present yourself can influence--for better or worse--other people's impressions of you, your values, and your ability to make smart and appropriate choices. People don't know how smart you are when they first meet you, but they can tell in a flash--based in some cases on nothing more than your appearance--that you've made some woefully bad choices sometime in the past. And it's a very short hop from there to "I don’t care," or worse.

We're still judging books and people by their covers. We're just drawing different kinds of conclusions from the data. Today it's less about economic circumstances or purchasing power and more about attitude, competence, and overall good judgment. This is not to say that you're not free to ignore other people's impressions and reactions and make your own choices; it's just to remind you that these are, in fact, conscious or unconscious choices that you're making, and that all such choices come with consequences. As you get older, you learn that who you are and what kind of life you get to live is largely the sum of all the choices, good or bad, that you've made along the way.

I recently wrote about one part of this problem in connection with the question of what to wear when you go on stage for your Demo Day pitch. I thought that your team's T-shirt was probably the safest bet of all, but mainly I was trying to suggest that you stay within the basic guidelines and avoid overdoing it in any direction. You don't want the way you're dressed to become a distraction. And the last thing you want to happen as you walk onstage is to have anyone looking at you rather than listening to you.

Crazy clothes, extreme high heels, and bushy beards all subtract substance, attention, and focus from your story. I realize that there are plenty of smart and savvy people who choose to dress or wear their hair in a certain style, but in this narrow context, I think a fashion faux pas can start you off with a crowd that wonders if you're serious. Why would you want to set out with that extra monkey on your back? This is a steep enough slope as it is; starting out in a rut of your own making makes no sense. You should "make your statement" in some other time and place.

There’s another monkey to avoid if you can. Good people (that is to say, most consumers) are somewhat patient, largely understanding, and--most important--inclined to give almost anyone the benefit of the doubt. But when you present yourself in a fashion that feels more like desperation than design or style--and you put it out there with an "I dare you to say something" attitude--you forfeit the benefit of the doubt.

Now the stakes are changed and you have to do everything else really well because you've essentially given up the margin of error. If you're going to be right up in my face, you'd better not slip up because it's a slippery slope and a long road back. Make the slightest mistake and the person standing opposite you changes in an instant from "Get-Along John" to "Judgmental Joe." People go from neutral to negative in these situations in seconds. We've all been there and done it ourselves.

So if you're going to have tats all over your body or nose rings in your nostrils, understand that you're walking a tightrope of your own making. On any given day you might make it across with no problem, but you've made the job a lot harder and more perilous than it needs to be. And don't think it's easy to fix the situation or repair the damage with a smile and a few sweet words. You can't talk your way out of problems that you behave yourself into.