Not much I can add here, however I've not too long ago completed IMCr training and test.
In line with what all others have suggested so far, I would check as many of the instruments as possible prior to taxi. If for nothing else than to reduce the amount of instrument set-up time during vital actions, thereby reducing time of the ground (especially significant if costs are brakes off to brakes on!). Also if as many nav aids/radios are checked and set prior to taxi the vital action of recapping and vocally stating what will need to be identified when within range IMO shows a little planning nous. That said there are one or two things that I'd like to suggest.
During the after start/prior to taxi checks, should a VOR be out of range whilst on the ground, perhaps your airfield has an ILS you could set and check that the instrument is actually working? Notwithstanding normal tune/ident/check/use procedures, if it does correctly pick up the ILS then I would believe there's a greater liklihood that it will work when within range of a VOR (a sanity check).
Remember also that NDBs are not line of sight. If your airfield doesn't have one perhaps a nearby airfield will? Again whether it was able to be checked or not during pre-taxi, a vocal 'ADF tuned to xxx, to be identified once airborne' is all that is needed during vitals.
My final nugget of inexperienced wisdom is that DME will tune to many aids: ILS, TDME, military TACAN. Thus for example if your ILS is on maintanance and hence nil positive ident, tune to something else for your static check if possible, re-set to a useful frequency with a vocal sanity-check as above.
As for taxi checks all of the advice has been given already. I'm only to add that the aircraft checklist, if a comprehensive post-start instrument check has been completed (something like I'm suggesting here), should be adequate. A big but... be prepared to carry out extra checks as you see fit if you are left unsure of any piece of equipment.
Edit:
Very quickly on OAT and 0deg isotherm: At some point during the checks, be they start/after-start/taxi/vitals, when 'pitot heat as required' comes up this is the perfect opportunity to explain to an examiner/self brief at what altitude the 0deg isotherm is. At this point you can state whether you can or cannot fly into icing conditions, is there any visible moisture, what FL/alt could you fly to before airframe icing could realistically occur, and what icing checks you will carry out in the air.
