The Behavior of 'gustar' and similar verbs
The first thing you should remember is that the sense of the verbs that behave like "gustar" (such as "enfadar" (to make mad), "molestar" (to bother), "irritar" (to irritate), "horrorizar" (to horrorize), "agradar" (to please), "hacer gracia" (to be funny to someone), "caer bien/mal" (to be pleasing to someone), etc., etc.) a lot of times implies that "something" [subject] influences [verb] someone [indirect object].
The same relationship will exist throughout the use of the different verbs. Remember that you can distinguish these verbs because they imply an emotional response from the indirect object. The indirect object either likes or dislikes in some way the subject. If it bothers you, then we can say that you dislike it, and viceversa.
In English you have this type of relationship for some of these verbs:
In this sentence, the shirt is acting on someone ("me"). For that reason the subject (shirt) and verb (bothers) are in agreement. When we translate it to Spanish, we can see the structure is basically the same and that the relationship subject-verb will remain the same.
The only thing that changed here is the placement of the object pronoun. While in English this pronoun remains at the end of the sentence, in Spanish it is placed in front of the verb. Some linguists say that the pronoun becomes part of the verb itself. Remember that the pronoun can be changed and the verb will not be affected in either language.
As in English, if you change the subject number, the verb will be affected since subject-verb agreement must always exist.
Notice how in English the verb lost the 's', distinctive of the 3rd person singular, because of the plural subject. In Spanish we must add an 'n' in order to maintain the agreement.
Whenever you have an action or actions as the subject, you should always conjugate the verb in the 3rd person singular, even if the previous subject remains in the sentence. Look at the English translation when it has only one action and you'll see that is the same as in Spanish. However, in Spanish, even when you have many actions, you still use the singular form.
Need of Definition of the Subject
You must also keep in mind that, when dealing with an object (not a person or verb), the object must be defined by the use of articles (el/la/los/las; un/una/unos/unas), possesives (mi, tu, su, etc.) or by demonstratives (este/esta/estos/estas; ese/esa, etc.).