Yo-Irregular Verbs

In the present tense most Spanish verbs are regular in the yo form (hablo, como, vivo), but a group of very common verbs is irregular right there.

• Go-verbs end in -go: tener → tengo, hacer → hago, poner → pongo, salir → salgo, venir → vengo, decir → digo, traer → traigo, caer → caigo, oír → oigo
• Most other verbs in -cer/-cir end in -zco: conocer → conozco, conducir → conduzco, traducir → traduzco, parecer → parezco, ofrecer → ofrezco
• One-offs: saber → sé, dar → doy, estar → estoy, ir → voy, ver → veo, ser → soy

The other persons follow their own pattern: many are regular (haces, pones, conoces), while tener, venir, decir and oír have extra changes (tienes, vienes, dices, oyes). Learn the yo form of each verb by heart.