Spanish makes a suggestion with the ordinary present tense rather than a special form: ¿Quedamos el viernes? is literally "do we meet on Friday?" and works as an invitation. Vamos a + infinitive covers English "let's", and ¿Por qué no…? softens a proposal into a question. You answer with vale, me viene bien, or lo siento, no puedo.
Examples
- ¿Quedamos a las ocho delante del cine?
- Shall we meet at eight in front of the cinema?
- Vamos a cenar juntos el sábado.
- Let's have dinner together on Saturday.
- ¿Por qué no vienes a mi casa?
- Why don't you come to my place?
The mistake to avoid
Don't use the future tense to invite: "¿Quedaremos el viernes?" sounds like a prediction about the future, not an offer.
Where this fits in
Planes y citas, Spanish A2: Proponer un plan, quedar con alguien, cambiar o cancelar una cita, y hablar del tiempo que decide los planes.