The main Wikipedia entry for Utilitarianism says:

Utilitarianism is the idea that the moral worth of an action is determined solely by its utility in providing happiness or pleasure as summed among all people. It is thus a form of consequentialism, meaning that the moral worth of an action is determined by its outcome.

Utilitarianism is often described by the phrase "the greatest good for the greatest number of people", and is also known as "the greatest happiness principle". Utility, the good to be maximized, has been defined by various thinkers as happiness or pleasure (versus suffering or pain), although preference utilitarians define it as the satisfaction of preferences.

Where 'preference utilitarians' links back to the short page on preference utilitarianism you referenced. That combined with the description of Peter Singer as the most prominent advocate for preference utilitarianism suggests weighted summing or averaging, though I'm not clear whether there is some specific procedure associated with 'preference utilitarianism'.

Merely satisfying your own preferences is a moral philosophy but it's not utilitarianism. Ethical Egoism maybe or just hedonism. What appears to distinguish utilitarian ethics is that they propose a unique utility function that globally defines what is moral/ethical for all agents.