Precedent is a judicial term describing the assumption that 1) if a higher court has ruled on a case with similar circumstances, the lower court must follow the higher court's reasoning, 2) that even the highest Court in the land, the Supreme Court, must follow it's own rulings in cases where circumstances are similar or the same.
There are three ways to rule around precedent for a lawyer or judge. The first is to show why the facts of law in this case are distinct from the facts of law in the prior case. This is the most common, and most effective. The second way is for the attorney to ask the court to reconsider the controlling precedent. In Lawrence v. Texas for example, the precedent was held by Browers, and so the court had to officially overturn Browers before they decided Lawrence v. Texas.
The third way can only be done by the judges, not the attorneys. That path is to simply ignore precedent. If a lower court does this, the case is likely to be overturned on appeal. If a single member of a higher court does this, it is allowed, but he or she will likely be chastised by the other members of the court. If the majority of the court does it, the Opinion will stand, but the court is tacitly saying "This is not a case that holds enough to truly sway us one way or the other". That is, they leave the door open for further cases on similar matters to attempt to decide exactly where lines may or may not be drawn. This third method has been used by Edwards in his decisions on Abortion, because he does not feel that Roe should hold precedent, but the cases before him do not present enough of an argument yet to change precedent.