You don't have to use nikkudim (plural of "niqqud"; I always use k, though, as does everyone I know.) unless you want to. It's used primarily for children, beginners and in religious texts. Essentially they act as the vowel sounds, but to an experienced Hebrew reader, they're usually not necessary. Occasionally one word or one letter in a word will have nikkudim if there might be a doubt as to which word is meant in that context.