Quick answer
voy a estudiar
ir + a + infinitive. This is the future you will actually hear in conversation.
The forms of ir
| Person | ir + a |
|---|---|
| yo | voy a |
| tú | vas a |
| él / ella / usted | va a |
| nosotros | vamos a |
| vosotros | vais a |
| ellos / ustedes | van a |
Only ir changes. The a is obligatory and the second verb stays an infinitive.
When to prefer it over the future tense
Use ir a for plans, intentions and anything close at hand. The -é future leans towards predictions, promises and guesses.
Note that vamos a + infinitive also works as "let us": Vamos a empezar.
In the past
Put ir in the imperfect and you get "was going to".
Memory trick
Three parts, always: a form of ir, the word a, and an untouched infinitive. Dropping the a is the one thing that breaks it.
Typical mistakes
Voy estudiar mañana.
Voy a estudiar mañana.
The a is not optional. Without it the sentence has no link between the two verbs.
Voy a estudio esta tarde.
Voy a estudiar esta tarde.
The second verb stays in the infinitive and is never conjugated.
Vamos a ir a la playa mañana?
¿Vamos a ir a la playa mañana?
A written question needs the opening ¿ as well as the closing one.
Check yourself
Mis padres ___ a visitarnos en julio.