Should I admit students who are waitlisted for my class? As an instructor at a large university, you will sooner or later have a waitlist for your class. Is it better (for you) to admit those students into your class or do you better keep the enrollment limit firm?

I favor the latter because it reduces my work, however marginally. What's more, it might improve the attitude of your students towards your class if there is more demand to take your class than you offer.

Is there a different perspective or a refinement of the above?
In my department for lower level courses I have no control over the enrollment of my classes.  For upper levels, it's rare the the capacity maxes out but here's a general way I would look at it from an instructor and/or administrator.


How frequently is the course offered?
There's a huge difference between a course only offered every year or two, and every single semester.  
Is the course required for graduation?
If not, there's far less reason to give the override.  If so, why stand in the way of someone's graduation (particularly if they're a senior)?
Are the other sections of the course full?
If the course has multiple sections, why don't they take one of those?  If there is a legitimate reason they can't (a required course at the same time) I might be more inclined, if not, they can take it the other one if they really want it.
Whose student is it?
My department has one to let majors and minors always take the classes, but those who are not in our department will only get it in exigent circumstances (must have course to graduate).  This is because we are penalized if our majors don't graduate on time and we need to always make any marginal spots available first and foremost to them.
Is there a general policy?
Your department may have a policy for this.  If so, use that.


I don't think that there is any benefit to intentionally reducing numbers to increase demand later on.  If your class is required, people will take it because they have to, not because it's popular (your department has created an artificial demand).  If your class is not required, then students will just find a different class and not bother with yours another semester.  The demand for a non-required class only tends to go up if it has the reputation of being easy, fun, relevant to other majors, or some combination thereof.