Best practices for solving location issues

[Gbg]

During the last days I spent considerable amount of time solving issues with my location definitions.
Sometimes I could see attempts to open files in the error.log, sometimes not. 

I know there is https://www.nginx.com/resources/wiki/start/topics/tutorials/config_pitfalls/ but wanted to ask if there is a list of best practice troubleshooting advice or even some tool or debugging switch that can help me find out which location gets used for a specific URL or URL pattern
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