Verb + infinitive
need to, have to, going to, want to, ought to, can do
In Spanish, the infinitive will end in one of three ways: -ar, -ir or –ir. In some cases, such as reír (to laugh) or freír (to fry), the vowel takes an accent.
Here are some random examples: abrir (to come), llegar, (to arrive), comer (to eat).
necesitar + infinitive - to need to do something
Yo necesito estudiar. I need to study.
Tú necesitas limpiar tu cuarto. You need to clean your room.
Ella necesita ir a la tienda. She needs to go to the store.
Él necesita lavar el carro. He needs to wash the car.
Nosotros necesitamos cuidar al perro. We need to take care of the dog.
Vosotros necesitáis pagar el taxi. You need to pay the taxi.
Ustedes necesitan buscar el dinero. You need to look for the money.
Ellos necesitan practicar los instrumentos. They need to practice the instruments.
Tener que + infinitive = have to do something
Tengo que comer las verduras.
I have to eat the vegetables.
Ángel tiene que leer el periódico.
Ángel has to read the newspaper.
Ellos tienen que comprar una revista.
They have to buy a magazine.
Hay que + infinitive = one must or it is necessary to do something
Hay que + infinitive is used to express the idea of "one must do something" or, "it is necessary to do something." It is a more general expression and since there is no subject, the verb form hay is always used.
Hay que tomar un taxi.
It is necessary to take a taxi.
Hay que estudiar mucho.
One must study a lot.
ir a + infinitive = go to do something
ir a + infinitive = to be going to do something (in the near future)
Voy a llevar a mi hermana a su casa. I am going to take my sister to her house.
Vas a invitar a muchas muchachas. You are going to invite lots of girls.
Cristina va a conversar con mi mamá. Christina is going to talk with my mom.
Eduardo va a leer el libro. Edward is going to read the book.
deber + infinitive = ought to do something
Deber + infinitive = suggesting that something SHOULD, MUST, or OUGHT TO be done.
Debo limpiar mi carro. I should/must/ought to clean my car.
Debes lavar las vajillas. You should/must/ought to wash the dishes.