I have written a .NET web Service that is to be consumed by a client outside of my control (my server is a simulator for a live server written in PHP). The web service work
You could also put it in a directory by itself, then in IIS set it as a default document.
On server: C:/mywebsite.com/mywebservice/mywebservice.asmx
In IIS set mywebservice.asmx as a default document
On the web: http://mywebsite.com/mywebservice