How should I respond/act with people who stutter when I personally do not?

How should I respond/act with people who stutter when I personally do not? There's a guy who comes into my work and he occasionally stutters. Normally it's when placing an order and rarely when saying hello/goodbye/etc. I don't want to offend him so /r/stutter, how should I respond? I have been acting like his stutter isn't there and by that, I mean I just look him in the eye whether he stutters or not. And if he stutters, I wait for him to finish and work it out and I never complete his sentence for him. Is this the proper etiquette?