are these coherent sentences?
¿qué vas a tomar de cenar?
nosotros servimos comida española.
quiero pedir otra cosa.
yo voy a pedir un pincho de torlla de patata.
are the verbs used correctly?
¿qué me recomienda? (is it "what do you recommend me')
¿qué serve de pescado?
the last two are spoken to a waiter, is it necessary to use the third person singular verbs to show politeness'
4 Answers
¿qué vas a tomar de cenar?
¿qué vas a cenar?
tortilla de patata
are the verbs used correctly? YES
¿qué me recomienda? (is it "what do you recommend me') YES
¿qué sirve de pescado?
¿qué clase de pescado tiene?
the last two are spoken to a waiter, is it necessary to use the third person singular verbs to show politeness' ---It would sound better but not necessarily. When you use tiene(Usted) instead of tienes (tu) you are already being polite. The same goes for recomienda (Usted) vs recomiendas (tu).
Regional limiter, as I call it. Sure I'll get flamed on that description. Anyway, alot of it depends on where you are, who you are talking to, what kind of mood they are in, etc. Anyone of those make perfect sense to me, since I am sitting in a resturant and this guy in front of me is clearly the mesero. 
Que vas a tener...Que te puedo llevar...Que vas a tomar (although tomar is usually used for drinking around these parts).
¿qué vas a tomar de cenar?
I used to use "tomar" in this way -- I was corrected several times to use "tener".
"Voy a la playa para tener almuerzo."
I have not been corrected since. It must be a local use. Any thoughts -- right or wrong?
They make sense to me. If you want to show respect, you want to use the "usted" form of verbs.
