Is something going wrong? Walk yourself through this checklist of common debugging techniques!
Check the response status code
400-level errors are client errors, meaning the API isn’t happy with your request. Check the API documentation and compare your request URL and it’s parameters.
500-level errors are server errors, means something is wrong with the server of the API. Wait a second and try again. If the problem persists, contact the owner of the server if possible.
Check the response body
Are there any error message clues in the response body?
Check the Postman Console (lower left)
Here you can see your raw network requests and responses, as well as any console.log() etc. statements in your scripts.
Are variables in your request URL resolving how you expect? Are you missing any parameters? Compare your request with the API documentation.
console.log() is your friend
If your problem involves scripting in the Tests or Pre-request Scripts tabs, use console.log(someValue) line by line to find out what is happening at each stage of your script. You can see the logged values in the Postman Console (see above)
Google it
Receiving a mysterious error like ECONNREFUSED? Google has answers.
Search this forum
The Postman forum is a gold trove of searchable questions and answers. Odds are someone has run into a similar problem as you! Topics related to Postman trainings can be found in the Training category.
Don’t see your question in the forum? Ask a new one! Post your new topic in the Training category if it relates to any of the Postman trainings. Your thread may help someone else struggling in the future 
More on debugging in Postman
- Troubleshooting Requests
- Powerful Debugging with the Postman Console
- Debugging with the Console | Postman Level Up (YouTube)
Debug boldly!