1. Log on as Farm Administrator.
2. Start SharePoint Central Administrator.
3. ​Click Monitoring.
4. Click Configure diagnostic logging (under Reporting).
5. Find SharePoint Foundation and expand the category.
6. Scroll to Web Parts and select  it.
7. Below the categories, you will find two combo boxes:
   1. Change the one labeled Least critical event to report to the trace log to Verbose.
   2. Click OK at bottom of the page.

Note:  After debugging, remember  to change this back as it will impede performance and fill up the log files faster. 
The Log is located in C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\LOGS. (For SharePoint 2013, the 14 is a 15.)

8. After the error occurs, find the LOG file with the most recent date/time stamp and examine the contents.
9. Use the Correlation ID from the error to find it in the log.
10. Using a tool like the ULSViewer can help with this since you can filter on the correlation ID. (A quick internet search for ULSViewer will locate that free tool to download and use.)

Operating System and Release Information