Ooooh ......... don't mention Project Managers Nono. lol
Recommendation every time if possible Whattie. If you're a stranger to the area, ask at a local builders merchants. They know who's popular, who's experienced etc. Also, if you're on good terms with your Building Inspector, he'll know who's reliable, and who would be suited to your particular project. Bad news travels fast in this business. You should soon know who to avoid.
When you talk to someone likely, simply ask what they've done in a similar vein, preferably somewhere where you can check out the finish etc. A good tradesman will always be keen to crow about what they've done. It's human nature.
Most people are "technically" capable of doing a job ........... more important is that you feel you can establish a rapport. It sounds cheesey, but a happy job is usually a good one. That's always been my experience. Attitude is 99% of the job.