Quick answer
hablo · como · vivo
Drop the -ar, -er or -ir from the infinitive and add the ending for the person. Three sets of endings cover almost every verb in the language.
The three patterns
| Person | hablar | comer | vivir |
|---|---|---|---|
| yo | hablo | como | vivo |
| tú | hablas | comes | vives |
| él / ella / usted | habla | come | vive |
| nosotros | hablamos | comemos | vivimos |
| vosotros | habláis | coméis | vivís |
| ellos / ustedes | hablan | comen | viven |
-er and -ir differ in only two places: nosotros and vosotros. Everywhere else they are identical.
Spanish drops the pronoun
The ending already says who is doing it, so the pronoun is usually left out. Hablo español — not yo hablo español. You add the yo back only for emphasis or contrast.
Three jobs English gives to other tenses
This is why “I am eating” needs no special construction. Spanish has one (estoy comiendo), but it stresses that something is in progress at this very second and is used far less than the English -ing form.
Memory trick
The yo form always ends in -o. Every regular verb, all three groups, no exceptions. If you only remember one thing, remember that.
Typical mistakes
Yo estoy hablar español.
Hablo español.
Two English habits at once: the “am” and the pronoun. Spanish needs neither.
¿Tú hablas inglés? — Sí, yo hablo.
¿Hablas inglés? — Sí.
Grammatically fine, but nobody talks like this. The pronouns make it heavy.
Check yourself
Nosotros ___ en Madrid. (vivir)