For my rehabs, I go with my property manager's go-to contractor. I think he may be a bit on the pricey side, but the management company feeds him a lot of business, so he doesn't want to loose their trust. Plus, he's been pretty fast, and complete's everything in a couple of weeks. Also, that contractor does pretty good work, and after doing a few rehabs for me, he understands what I'm looking for.
I think the old adage goes "you get what you pay for." After seeing and hearing a lot of horror stories about flakey contractors, I figure that even though I may be paying 20% more than I could, I know that the unit will be tenant ready in less than 30 days, and I don't have to worry about someone not finishing, sub-par work, or other issues.
In your case, if you have a property manager, see who they use on their projects. Reputation is built through experience, and experience through volume. PMs get a ton of volume, so they're a good resource. Even if you are self managing, you may try to just call some PMs in the area and ask for contractor recommendations.
As for process, I would recommend that when you do find a contractor that's highly reputable, you give them general guidelines, and let them do what they do best. Don't be overly-prescriptive on types of materials, because that interferes with their supply chains and internal methods. Instead, simply offer them the look and outcome you are going for, and let them do the rest. Don't say "I want you to use these materials in this way for this price and this timeline." Instead tell them "I'm looking for neutral tones, hardy material, and this budget...what are my options?" After that, step back and be pleasantly surprised with the outcome. Remember, they do this a lot more than you do, and are probably better at it than you too! If they enjoy the freedom you give them, then they are more likely to want to work with you in the future, and start moving you up the list of clients to keep happy.