A conflict of interest is a situation in which you cannot fulfil your duties to one party because of your obligation to another party. A television station experiences a conflict of interest when reporting on scandalous activities on the part of one of their sponsors because it is in their duty to tell a truthful, unbiased story but it is against their best interest to make their sponsor look unfavourable. The best course of action when facing a conflict of interest is to be truthful to everyone involved and, if possible, excuse yourself from the situation.
Identify your interests in the particular situation. If you are a judge and your wife appears in front of you as a lawyer, you would have interests in administering justice as well as in pleasing your spouse.
Evaluate whether your loyalties to the different parties creates a conflict which makes it difficult for you to fulfil your duties to either party. The judge whose wife appears in front of him as a lawyer compromises his commitment to justice because his interest in pleasing his spouse interferes with his ability to impartially administer justice.
Evaluate whether your loyalty to one of the parties is so distant or so generic that it will not actually interfere with your ability to act impartially. For example, a reporter writing about the effects of global warming has an obligation to tell the truth as well as a personal interest in the story as a human being who could be affected by global warming. But his loyalty to his own interest as a human being is so generic that it does not constitute a real conflict of interest.