Once you've picked a namespace you're stuck with it. Is there any good articles on how to specify (and maybe version) a namespace.
Should it use it's own domain?
I could just use www.ecs.soton.ac.uk/mynamesapce
Should the namespace resolve to an RDF+XML document describing it, or should it use 303 See Also?
You might find this W3C Working Group Note helpful: Best Practice Recipes for Publishing RDF Vocabularies.
This document describes best practice recipes for publishing vocabularies or ontologies on the Web (in RDF Schema or OWL). The features of each recipe are described in detail, so that vocabulary designers may choose the recipe best suited to their needs. Each recipe introduces general principles and an example configuration for use with an Apache HTTP server (which may be adapted to other environments). The recipes are all designed to be consistent with the architecture of the Web as currently specified, although the associated example configurations have been kept intentionally simple.
+1 for the best practice doc pointed out by jackem - after this, you might also want to coin a prefix and 'register'/announce it at http://prefix.cc/ ...
The "Best Practice Recipes for Publishing RDF Vocabularies" is a very good resource for handling this issue. However, this documentation is also a bit out-of-date. It should especially include the handling of different Semantic Graph (RDF) representations (serializations), e.g. turtle/n3 or JSON.
Furthermore, I thought a bit more about, when it might be better to use '/' URIs or '#' URIs. I came up there with the following requirements/features through my observations. I would tend to propagate '#' URIs for T-Boxes as it is also described here for the majority of ontology specifications. These specifications share the following features:
However, if one of these features (requirements) is violated, then it might be better to split the ontology specification description and use '/' URIs as it is also described here. One could apply these features also to A-Boxes in my mind.