How can I debug an 'npm run start error' if the error message is vague?

If the error message isn't helpful, try running the 'start' script directly in your terminal (e.g., `node server.js` if that's what your script does). This often provides more detailed error output. You can also add `echo` statements within your `start` script to trace its execution and identify where it's failing. Consider using a debugger like Node's built-in debugger or VS Code's debugger.