Spanish verbs that end in –uar are conjugated with the same endings as regular -ar verbs, but most –uar verbs require an acute accent (tilde) on the u in certain forms of the present tense, subjunctive, and imperative.
-uar verbs
All –uar verbs except those that end in –cuar or –guar need ú in all but the nosotros and vosotros forms.
Spanish verbs that end in –guar do not have an acute accent on the u, because that letter is not stressed. However, because these are spelling change verbs, a dieresis is required on the u in all the conjugations where it’s followed by e in order to maintain the correct pronunciation.
Spanish verbs that end in –cuar are exceptions to all of the above: they do not have any kind of accent on the u, and are thus conjugated exactly like regular –ar verbs.