I wrote about this once before, years ago, when i published a dead tree magazine, but it bears repeating as i am often asked the question "when is the best time to go into a restaurant if you want optimal service?" People seem to think that i have inside information or something.
Suppose your beanery of choice operates from 11 a.m. 'til 11 p.m. Going in right at opening time is no good, because the staff are most likely still scrambling to get everything ready, and will be unable to give you the attention you deserve.
Between, say, 11:30 & 1:30 is not a good idea, either, because the lunch service is at its height and the staff are too harried to pay much attention to you. (Unless of course it's a crappy restaurant to which no one ever goes, but then, why would you want to go there?)
OK, then, mid-afternoon. Er, nope. The kitchen staff will be busy getting ready for the dinner service and the servers will be relaxing and smoking and gossiping and won't appreciate the interruption. Sorry.
All right then, how about at dinner time? Well... no. For the same reason that going in at lunchtime is ill-advised: everyone's too busy.
So, later on in the evening, after the dinner rush is over, then? Well, gee, i hate to say this but that's pretty much out of the question too: everyone's tired (some of them will have been there since before 11 a.m.) and they all want to clean up and go home.
So my advice? Go in whenever the hell you wish, but if the server (or, less likely, the cook) <wink> screws up your order, don't get annoyed, accept it. (And this applies especially if you have ordered something that isn't on the menu!)
(I see that there's a movement afoot amongst some of the best chefs -- the refusal to cater to special requests. I agree whole-heartedly even though i'm just a grunt in a chicken joint. The point being, according to the chefs, that they created the dish to perfection to begin with; saying you want extra havarti or no chestnuts indicates that you are a charlatan and you deserve to be tossed out on your arse!)