How do you know you can really trust your surgeon for rhinoplasty?

When a truly excellent surgeon has a dissatisfied patient, it's almost always because the patient achieved less improvement than she and the surgeon were hoping for. It's just about never the case that something went off the rails and the nose looks completely wrong.
An excellent surgeon can evaluate your particular situation and give you a good idea of what might go wrong, and the likelihood. He knows which features are more predictable to change, and which are less.
You limit your risk by doing an excellent job of selecting your surgeon. Be sure to read the section in the "Learn more" link on how to stay out of trouble while searching for a rhinoplasty surgeon. You should only have surgery if you are able to make yourself very confident in your surgeon's skills. 
I usually make computer morphs when I'm answering questions like this, to show the changes that are possible for a nose with a rhinoplasty, but of course you didn't post any photos. At the *very* bottom of the "Learn more" page is a link to instructions on taking and sending photos that are comprehensive and useful for an online consultation like this, in case you'd like a more complete evaluation.

Your concerns are very real. I would select your rhinoplasty surgeon based upon experience, their ability to correct any issues that might be required as in revision procedures and  what costs would be involved if that should transpire, certification by the American Board of Facial Plastic & Reconstructive Surgery or American Board of Plastic Surgery, photographs of previous patients including staff members. My personal approach is not one of "cookie cutting" as I do not have a one size fits all category for rhinoplasty. I think the nose should look as natural as possible and most people should not be able to tell if you have had your nose corrected or not. Some surgeons, unfortunately, have one approach to all of their rhinoplasty procedures. My approach depends upon each person's unique anatomy and I also believe that less is better and often the best results  and most predictable results are obtained when less surgery rather than more surgery is completed. Good luck with your decision.

First you have to make sure you have a doctor with the right training.  They should be certified by the American Board of Plastic Surgery or the American Board of Facial Plastic Surgery.  There are many other board certification types, but they don't apply to this surgery.  Next, check to make sure the board certification is real.  Yo can do this on plasticsurgery.org, surgery.org, or abms.org.  This will mean you have the right person, but of course, as you said, it does not answer the question of aesthetics.  For that, you will have to visit the surgeon you've looked up and speak with them to find out if you like their approach, their plan, and their prior results.