Cut the hide from the base of the ribs (deer don't have "collarbones" LOL) all the way around to the backbone just behind the front shoulders. Now peel the hide over the shoulders (you will have to split the hide from front leg ankle back to the original cut you made at the ribs, can be peeled all the way down to the ankle but not necessary and a lot easier to split) all the way down to right behind the ears, now cut the neck meat and the neck bone here as close to the last vertebra that you can. Taxidermist only needs the skull, hide and horns and all in one piece, he will split the hide and skin the skull/face to his own liking and experience as to how he needs it for re-creation. . Now take a tape measure and measure around the neck in 3 0r 4 places, rutting bucks can vary a lot in "neck swell" and your taxidermist will need these measurements to order a similar sized "mount form" to build and re-create your deer as he was when he stood in front of you.
The caring for after the skinning job is as important to safeguard the hide quality for the taxidermist...idealy you would want to deliver the head to taxidermist within a day of skinning the animal. If that's not an option (wilderness hunts that is never possible) then you have to freeze the head & hide ( roll the hide up behind the ears, not over them, you don't want to fold or bend the ears while they still have the ear lining in them...they will be a b!tch for your taxidermist to skin out) or salt the whole thing copiously with just plain household salt...when you think you have enough salt on ...double it. A hide that has "hair slippage" is worthless to your taxidermist.
It might sound like a lot of friggen around but it's not really, you have to skin the front of the animal and remove the head anyways so that's not even an issue and the salting will take 20 minutes at the most.