Depending on the kind of improvements you want to achieve, you need a solid Masterplan. This plan should be the guideline for all the work done at the golf course. Especially if changes and improvements are made step-by-step over a longer period of time, the Masterplan gives direction to the process.
In my opinion, a golf course architect should have the lead in developing such Masterplan, in close co-operation with an agronomist and if necessary a landscape architect and/or a consultant in the field of environmental issues, permits et cetera. At least that is the approach we took as Greens Committee at our club. It takes a lot of time and effort before you get started, but in the end it really pays off.
The selection of the golf course architect is another thing that needs close attention. What's the nature and character of your golf course, in what direction do you want to go, do style and experience of the architect match with that? These questions should be answered before hiring or even inviting an architect. To often, the selection of an architect is made on the basis of hearsay, the work done at a course close-by or because he or she happens to be fashionable. it is like hiring an architect for renovating your house. if you have a cosy villa in traditional, classical style, you don't want to have an architect who is a dogmatic modernist (and the other way around).
In other words: for your own sake, and for the sake of the architect, you should have a clear picture where to go, before you go out for a walk on the golf course.