Step one is examining why you want to have rhinoplasty. Cases in which the nose was damaged or the patient has breathing difficulties are not strictly cosmetic. If you would like purely cosmetic surgery because you don't like the look of your nose, or think it could look better, make sure you won't regret it. Don't have a nose job because your partner wants it, for instance.
Step two is finding a reputable plastic surgery clinic. This is extremely important. In many countries, including the United States, clinics that are not reputable still advertise very publicly. See if the clinic is associated with professional associations, and check that the surgeon that would perform your rhinoplasty is a licensed MD who has specialized in the relevant field. Don't take their word for it; do your research.
Step three would be discussing exactly what changes you would like to see, and gaining the surgeon's honest assessment on whether this is possible. You can have only the tip of your nose operated on, or you can have more radical surgery that involves reshaping the bones. Recovery time and post-op pain will vary accordingly... as will the price of your surgery. Make sure that your surgeon understands your wishes before you go ahead. But, also know that you will never know exactly how surgery will turn out beforehand. You will have a different nose, but probably not exactly as you envisaged.
Once you have decided to have your op, and have booked the appointment, obtain a list of what you need to do beforehand. This will include not smoking cigarettes two weeks before the operation, not taking certain medications (including Aspirin), and taking a few days off work around the time of the operation. Rhinoplasty patients will need someone to drive them home after the surgery, and will need to spend a few days doing nothing followed by a few weeks of taking it easy. This is convenient, because you will probably not want anyone to see you before the bandages come off usually a week post-surgery anyway.
Also discuss the post-op requirements with the surgeon or nurses at the clinic, and follow the advise closely. You will also need a follow-up appointment to make sure everything went according to plan.