Hmmm, there's loads of things you may decide need doing whilst you've got the clam off - but I'll let you think about them whilst you're doing it!
The process is simple and straightforward (as per the Workshop Manual), but having done it myself, I can add the following words of (not real) wisdom....
The headlamp motors need to be removed, and the bolts for these are removed with a small (1/4" drive ratchet, 8mm socket) bolt which is withdrawn into the wheelarch - so the liners need to be removed (which they need to do anyway to get to the clam to 'A' post nuts/spacers/bolts) - it is worth having a new set of fasteners (for the liners) on hand for replacement in Stainless Steel (if you haven't already replaced them)... it is a good time to inspect and/or replace the 3 plastic 'pills' inside each motor whilst they're off the car.
When the whole lot (clam shell fixings) have been undone it should easily lift away from the car - if it doesn't, check that you haven't missed one (easilly done - from experience) - the only other thing holding it in place is a thin bead of sikaflex at the bulkhead - it needs carefull cutting through with a Stanley knife.
When lifting it from the car, an assistant is invaluable (more so when replacing it after painting!!!!!) - otherwise it can be easy to catch it on the suspension tops and/or twist it and cause cracking.
ALWAYS observe/record how many shims you have in various locations (mainly between crash structure and clam) - it'll save a lot of trial and error on refitting.
Whilst it is off, have a good look at the M6 bighead bolts which come up from underneath (so can't be got at with it all back together - but some access is possible with the front bumper removed), and attach the bottom of the headlamp hinge mechanism - mine had rusted badly, so i replaced them with new stainless items whilst it was off the car - you can just use 'normal' bolts, but you will need to be able to hold the end still to do the nut up, so the proper 'captive' items are worthwhile - likewise the captive cage nuts which the bonet adjustment bumpers fit into.
Basically, i'd advise swapping every nut,bolt and fastening with Stainless whilst you're doing the job - it'll look so much neater in a newly painted car anyway
You'll no doubt find that so many other bits are really easy to get at with the clamshell off the car, and will be removing and cleaning all sorts.... just remember to replace them before fitting the clam, or they may not be so accessible afterwards (Charge cooler, air intake etc springs to mind).
Changing the belts/waterpump etc is sooooo much easier with the clam removed, I'd even consider whipping it off to change them in the future (especially with new nuts and bolts which come undone easily!).