The neck should be as you would expect for the type of work you want the horse to do. A short thicker neck would indicate a lot of power whereas a longer arched neck would indicate elegance. If the neck dips in front of the withers, it will tend to make the horse quite ewe necked, this will make it difficult to achieve the correct outline in ridden work and also give the horse a more hollow back when ridden and especially jumped. You should look for a good length of rein, ideally you do not want the horses head in your lap when you are riding it. If the distance from the front of the saddle to the bit looks short then there will be a tendency to have a lot of rein not in use.
Personal taste varies.
There should be an unbroken curve from the poll to the withers. The shoulder should not appear to have too straight a line at the front of it. A straight shoulder often gives a choppy up and down movement from the paces, this is quite uncomfortable to ride on. However it is quite desirable in a number of driving breeds. The whole shoulder should be well muscled without being too heavy in appearance.