In reply to Carpe Diem:
For the best experience I'd say camp it (wild wherever possible, maybe the odd campsite if it's convenient).
Carry your own bag (you're more flexible than with a bag carrying service and this is particularly needed if you're wild camping and stopping just wherever looks good). Go light, but only within reason. You'll need to plan ahead for where you can get supplies - there aren't that many shops en route so you may end up carrying a couple of days' worth of food at times. Pub dinners are a good idea.
Lightweight comfy footwear: big clumpy boots are a pain on the hard packed surface. Most of the WHW is hard and well drained underfoot.
Best sections: Conic hill, and along east shore of Loch Lomond (note wild camping is banned south of Rowardennan). Bridge of Orchy to Kingshouse. Devil's Staircase to Kinlochleven. the first bit of the day from kinlochleven to Ft.william (2nd half is dull forestry). Some of the rest is a bit disappointing, in that you're near a busy road and hemmed in by fairly dull grassy mountainsides or forestry - just put your head down and get it over with, there's always a better bit round the corner. I'm really not sold on the first day from Milngavie to Drymen but it's a gentle countryside contrast to the mountains I suppose, and you do it for the sake of completeness... Be prepared for the finish to be a bit of a nothing; no offence to Ft.william but the WHW is more about the journey than the final destination.
Timing-wise, five days is reasonably ambitious, but realistic. You can do it in fewer or stretch it into more. I'd suggest adding a couple of days to the schedule in order to climb a hill or two. WHW goes low the whole way (OK over a couple of passes) so it really misses out on the best thing about the area, which is the mountains. There are plenty of cracking hills adjacent to the route. Ben Lomond, Ben Lui, Beinn Dorain, Stob Ghabhar, Buachaille Etive Mor, the Mamores and of course the best way to crown the walk is an ascent of Ben Nevis...
The Harvey Map to the West Highland Way is all you need for planning and the day to day walking, but of course it does not cover the surrounding land so if you're hoping to do detours up hills you'll need the appropriate OS sheet(s).
Route finding is not an issue. You don't need to consult the map at all to find the way - just look at it once in a while to place yourself
and work out how far to the next pub.
Guidebook not really necessary but it does help with planning and working out where to find facilities etc. The Pocket Mountains guide has all the main hill routes as well as the WHW description, so that makes it the best of the books. But I would say that, I wrote it.
