So I've started this list to make sure I don't spend so long anymore on debugging code. The aim of this article is to quickly suggest ways of pinpointing the source of the problem:

In a database/web environment, have you?

1. Commented out lines that you suspect might be the problem?
   
   
2. Able to run the SQL queries directly against the database?
   
   
3. Matched the datatypes received/returned by functions, classes and procedures?
   
   
4. Confirmed any ACL/permissions on the files?
   
   
5. Ensured all global, posted and session variables are present when they should be and behave properly?
   
   
6. Broken down the error in understandable and diagnosable parts?
   
   
7. Checked appropriate services are running?
   
   

Questions for the customer

1. Can you access the service?
   
   
2. Can you open other similar files in the same environment?
   
   
3. Is a colleague experiencing the same issue?
   
   
4. Can you access the service using a different workstation?
   
   
5. Was the last time you used the service recent?
   
   
6. Has anything been installed on your workstation since the service last worked?
   
   

Suggestions by Wikipedia

1. If you are having difficulty understanding a problem, try drawing a picture.
   
   
2. If you can't find a solution, try assuming that you have a solution and seeing what you can derive from that ("working backward")
   
   
3. If the problem is abstract, try examining a concrete example.
   
   
4. Try solving a more general problem first.