Well..... it depends :)
There are places that body clip their horses year-round, and just add blankets as needed. If your horse gets hot enough during work that the coat is causing discomfort, I would say clip away.
If you go for a full body clip, I recommend against clipping everything. Leave the legs natural and trace the saddle pad area and leave that natural. Reason being is that the horses legs will not have protection from the cold from a blanket, and many horses get irritation from the saddles/pads when they're clipped there.
If you're not sure that you want to jump straight into a full body clip, then you have several options available to you. Here's some: Peasridge Clipper Advice - Clipping Advice - Horses
The names of the actual clip styles can vary, so if you're hiring someone to do a clip for you, make sure that they show you what they're going to do. You can also do variations of these clips -- you can leave the head unclipped, or clipped, or change the lines a bit. But the diagrams are a good start.
There's no real set of rules on clipping. People do or don't do it for various reasons -- including our convenience. I body clipped my horse last year because he only grew enough coat to take hours to dry, and I simply didn't have 3 hours to wait for him to dry off. I clipped him, added some more blankets and he was good to go.