Bike prep - read some of the SSDT bike prep articles written by John Lampkin and John Shirt - especially keeping mud out of rads and air box etc.
The monts are sturdy beasts so a good general fettle - check fluids, new brake pads, spokes, linkages etc - a larger bash plate f not already fitted or the SSDT type protectors etc.
I found last time that the enduro / motorcross type donuts on the grips helped reduce blisters .
Would suggest getting the bike sorted a week or 2 in advance then ride it to make sure everything bedded in and tight -then just a good once over the week before.
If you can find a bit of land with stream sections and a biggish lap with moor work or similar then just practice ridding it for several hours without stopping - when you can do that for a few hours and still feel ok youl'll be ok to the first petrol stop ..