Let's be blunt: ghostwriting may be the single most unsatisfying type of work that a writer can do, for the sole reason that you can almost never take credit for it. This hurts more than ever when you are fortunate enough to have particularly good content to work with and produce a truly exceptional piece...only for someone else to claim your wonderful creation as their own.
Unfortunately, that's part and parcel of the job when you choose to undertake such a task. A writer's work is generally dear to them, but when you write for someone else, you are doing so with the understanding that your work is no longer your own, and that can be tough, especially for those who are new to the process.
know your worth, author's voice, let it go (no credit), interview, know their voice, pull together the information into themes, know the material/research, respect their experience/expertise, don't embellish, do explain concepts for laymen where needed, choose genres/subjects you aren't attached to or even prefer not to be associated with