"We are waiting for the waitress."
We usually don't use "için".
Beklemek is a perfectly transitive verb in Turkish. Just say whatever you're waiting for and bob's your uncle.
I think that "for" is a Germanic thing. English, German and Danish all use a preposition after the verb "to wait"; wheras French, Italian and Spanish don't use anything. Neither does Turkish.
So if your native language is English, this is one of those verbs that you have to be careful about.
Another way to think of the verb beklemek for us English speakers is to define it mentally as "await." If you use that definition, then you don't use "for": "We are awaiting the server (or waitress or whatever)." That might help. (Even though we seldom say "I am awaiting." But it might help you think how you don't need the "for" or "için."