I have a plan for the future for an application and web service. The client will have an application that will send requests to a server-side Java back-end that will process requests, and the server should also be able to host a website, preferably on a WAMP setup (which is what I'm used to; very little *nix knowledge).

Now, I cannot provide any hard stats because this is only a plan that's in a discussion stage. However, we do fully expect it will scale enough to need some type of dedicated hosting.

My question is this: what types of things should I know about before looking into getting hosting? What should I be asking the hosting providers before I decide on a purchase? When is it appropriate to switch from a VPS to a fully dedicated server?