At the outset, I want to make clear that I have no inside information regarding bar admissions, other than my own experience in the process. As a threshold matter, I would encourage you to always honestly and candidly deal with any issues in this regard with the bar authorities. Additionally, most have comprehensive websites, complete with the underlying statutory authority upon which the requirements are based, and that you should consult, in order to evaluate your particular situation.
As part of your bar examination process, you will be required to fill out an incredibly comprehensive application (most likely, complete with a fingerprint card). The application will take a fair amount of time to complete and require information that you may or may not have at your fingertips. So, as will all things law school, be prepared to spend a fair amount of time on the application, and do not wait until the last minute to begin the process. This application will become the basis by which the bar examining authorities will investigate whether you have the requisite character and fitness to practice law.
But you should also know that bar authorities are also understandably unwilling to prognosticate as to your ability to ultimately receive a license. There are too many variables involved in the calculus and until the actual character and fitness investigation is completed, it would be extremely irresponsible to say, for example to a candidate that a particular incident in high school would not prevent them from obtaining a license. That incident would be weighed against a variety of factors, which can only properly be weighed in the context of a variety of other factors- age at the time of the incident, recency of the conduct, evidence of rehabilitation, other incidents, etc.
For most new lawyers, about the only other license they've had is a driver's license. As with a law license, the ability to drive is a privilege and not a right. In other words, the presumption is that you should not be allowed to drive; you must overcome this presumption by showing that you have the necessary qualities to operate an inherently dangerous 3000 pound machine at seventy miles per hour. With a law license, you are entrusted with something of even greater risk- people's lives, and you must show that you are capable of such trust.
Obviously, you must show that you possess the minimum competency to practice law. You do this by passing an extremely lengthy and difficult bar exam. But, as a threshold matter, before you are even allowed to sit for the exam, you must show that you have the fundamental character and fitness required of all lawyers. You do this by submitting to what is essentially a comprehensive background check administered by the bar authorities and their designates. This application is available in many jurisdictions online.
What is the requisite character and fitness to practice law? Different jurisdictions define it in different ways, but the core of the definition is what you would expect it to be: honesty, trustworthiness, diligent and reliable, in order that the lawyer in question can be entrusted with a clients affairs, as well as the operation of the legal system (see, e.g. the Minnesota Board of Law Examiners website, http://rly.cc/aFf7i).
Generally, the bar admissions authorities look at whether a candidate has a history of dishonesty, unlawful conduct, academic misconduct, neglect of financial responsibilities, misconduct in employment, violation of a court order, emotional instability or drug/alcohol dependence, in making the character and fitness determination (see, e.g. the Texas Board of Law Examiners website, http://rly.cc/ojWZL).
The single, best piece of advice I would offer is that you should be absolutely, painfully and completely candid and honest on the application. As most bar examiner websites indicate, an "incident" that you disclose may or may not be evidence of insufficient character, however, a lie iwould be. So the lie becomes worse than the incident itself. Additionally, it behooves you to read the application very carefully, which after three years of law school, should not be a problem for you. Make sure that you answer every question completely; one can lie not only by comission, but by omission. As a lawyer, honesty is the cornerstone of everything that we do.
If you have concerns that something in your background could be problematic, refer to your state bar's website. Review the rules and regulations regarding admissions. If you think you have a big problem, there are lawyers who deal with these types of issues; consider consulting with one.
Regardless, and at the risk of over-generalizing, probably the most important conduct is that which you engage in for the next three years (remember that the requirement is typically whether you posess the "present character and fitness" to practice law). There really isn't much you can do about that pecadillo in your past, other than put as much temporal distance between you and it as possible. Instead, you should focus on how, going-forward, you can be the best person you can be.
I offer the following suggestions for you to consider throughout your law studies, as "preventative" measures, and in the hopes that you will avoid the worst of all scenarios- a problem that occurs while you are in law school, that either delays or prevents you from obtaining a license:
1. Alcohol abuse- Law school is stressful, and unfortuately, there is an abundance of opportunity to abuse alcohol. Friday night "Blackacres" and the like, with low-cost beverages, which may seem benign (because "everyone's doing it") could result in a law student's DUI and public intoxication charges. Worse, repeated use of alcohol to deal with stress avoids the problem itself, and may set you up for progressively worse and perhaps even a lifetime of alcohol abuse. This abuse can lead to a myriad of other problems- client neglect, marital problems, health problems, the inability to focus, in short, issues you do not need to be dealing with, while working in an extremely demanding field.
2. Social Networking Websites- Internet "anonymity" has created huge problems for an entire generation of bloggers, Facebookers, MySpacers and Twitterers. Internet relationships create the illusion of anonymity and yet intimacy that tempts people to do and say things that they otherwise would not (say, for example, in a church study group). As a result, people post things on the web that they later regret. Unfortunately, the internet is forever. Anything you post goes into a server somewhere, waiting to later come back and haunt you. Regardless of what you may have posted in the past, consider cleaning up your blog, website and social networking sites. Some jurisdictions such as Florida, have announced that they will consider social networking sites as part of their character and fitness analyses.
3. Law School- Don't cheat. Don't plagarize. As simple as it may seem, every year some promising law student does something stupid enough to get thrown out of law school. Your law school probably has a Code of Conduct. Make sure you understand it and honor it completely.
4. Fiscal Fitness- Pay your bills when due. Don't overextend yourself financially. Your credit history will likely be a part of the character and fitness examination. As a lawyer, you may be entrusted with your client's money. If you cannot manage your own, it is unlikely that you will be able to manage others' money.
5. Obey the Law- As a lawyer, you are expected to uphold the law; both the big laws and the little laws. Now is not the time to get into fistfights, steal or do other similarly adolescent things, that to many are innocent pecadillos.
And if you want to maximize your law school experience, be sure and read my book, Law School Labyrinth- A Guide to Making the Most of Your Legal Education (Kaplan Publishing, March 31, 2009).