How is probability calculated when all outcomes are equally likely?

"A common special case occurs when all outcomes are equally likely. This usually happens when we roll dice, flip coins, or deal cards, since the probability of rolling a 3 is normally the same as rolling a 6, and the probability of being dealt the 10♠ is the same as the Q♦. It may also happen when we generate encryption keys, choose between alternate network routing paths, or determine the initial positions of enemies in a first-person shooter level. If there are N possible outcomes, where N = |Ω|, then the probability of any event A is Pr(A) = |A|/N. It is the size, or cardinality, of the event set that matters, and the ratio of this number to the total number of outcomes is the probability. For example, when dealing a card from a fair deck, the probability of drawing a face card is Pr(F) = |F|/N = 12/52 = .231. This shortcut only applies when the probability of each outcome is the same. We could not say that the probability of a user’s password starting with the letter q is 1/26, because passwords surely do not contain all letters with equal frequency. The only way to solve a problem like this is to know how often each letter of the alphabet occurs."