How do I know if I need to use the subjunctive in a sentence?

The subjunctive is used to express a variety of attitudes such as uncertainty, possibility, emotions and desires. In Italian there are four subjunctive tenses, but in English subjunctive forms are rare and usually old-fashioned (for example: if your father were here, he would be happy). The easiest way to form the present subjunctive is to start from the present tense and change the IO form. The -ARE verbs endings are: i,i,i,iamo, iate, ino. The -ERE and -IRE verbs have identical endings: a,a,a, iamo, iate, ano. We should never forget that there are many irregular forms and they need to be learnt.