How do you form the subjunctive?

Take the eu form of the present tense and remove the final -o. For -ar verbs, add the endings -e, -es, -e, -emos, -em. For example, the subjunctive of falar is eu fale, tu fales etc. For -ir and -er verbs, add the endings -a, -as, -a, -amos, -am, for example, the subjunctive of partir is eu parta, tu partas etc. Some verbs have irregular subjunctive forms which need to be learnt, such as ser (sej-), estar (estej-), ir (vá), saber (saib-).