If you have a true job offer in hand, the first thing you need to do is decide whether the offer is acceptable to you in its present form. In other words, if the offer as given is the very best you can negotiate, will you still accept the job? If not, you will need to take a different approach.
Job offers do come. Really, they do!
In either case, it is always important to know who is pulling the hiring strings. Not just making the decision, but also making the decisions about the offer components. This is usually the Hiring Manager, but not always. Hiring authorization may actually come from a level above the Hiring Manager. There may also be input from a Salary Administrator or Compensation/Rewards Consultant in Human Resources, although they are usually there for input, not for absolutes. The key is to know who makes the final hiring and offer package decisions. If you don't know, ask. Ask the Hiring Manager, the person for whom you will be working. Remember, it is always in their best interest to make this happen. Now that they have made you a job offer, you have one foot in the door to their company. You have access to information you did not have prior to the offer.