Most criminal cases begin when someone has a lapse in judgement, or is under the influence of drugs or alcohol. After the crime occurs, they go through the system, sheepishly, accept their conviction, and go on to find it is virtually impossible to get employment.
So first, avoid criminal behavior! Make choices that make it unlikely you will have a conversation with the police.
However, when one does get charged with a crime – protecting your record begins with consulting an experienced criminal defense attorney immediately! Pursue any alternative program that allows one to avoid conviction.
For instance, if one smokes marijuana and gets caught there are two likely outcomes (assuming that the police acted lawfully and there are no search and seizure issues):
One pleads guilty, pays a small fine, loses one’s driver’s license, and has 30 days probation, and receives a conviction that will be on their record until they file for a Pardon!
One applies for ARD (or section 17 disposition, in the past), receives 30 days probation, small fine, no license loss (possibly), and the charges are dismissed upon completion. This resolution allows an expungement immediately!
Two drastically different outcomes based on knowledge of the law and the system. Always consult an experienced attorney if you get in trouble. Better yet, avoid criminal behavior.