"He is a waiter."
Translation:Il est serveur.
In french, when identifying someone's profession or national identity the indefinite article is dropped. So I would say "Je suis professeur" or "Je suis Américain".
The exception to this is the use of "C'est" or "Ce sont".
A good explanation can be found here: http://french.about.com/library/weekly/aa032500.htm
Since serveur is a profession it follows "profession" rules for pronouns: either "c'est un serveur" or "il est serveur". Much like c'est un prof or Il est prof. Why? I don't know for sure, though my hunch is that may have to do with pronunciation- "c'est un" (with the pronounced t) flows better than "il est un... and french is nothing if not flowy ;)