This is the list of steps to follow for troubleshooting general SharePoint issues.
1. Turn on the debug flag from SharePoint web.config
Note: Enabling debugging is not recommended on a production environment.
a. Locate the SharePoint web.config file which is typically located under one of the virtual directories in C:\Inetpub\wwwroot\wss\VirtualDirectories.
b. Make a backup of the web.config just in case.
c. Open the SharePoint web.config using a Visual Studio or a text editor such as notepad.
d. Find “CallStack”
e. Change the value of CallStack to “true”
f. Find “CustomErrors”
g. Change the value of CustomErrors mode to ”off”
h. Save the web.config.
2. Reproduce an issue you’re having i.e. by refreshing the broken web page
3. Examine the error from EventLog. In most cases, you will find no useful information from EventLog since SharePoint does a poor job leaving a trace on the EventLog.
4. Go to SharePoint logs folder (c:\Program Files\Common Files\Microsoft Shared\web server extensions\12\Logs). SharePoint dumps all logs in this folder, and so you should be able to find clues by examining logs in this folder.
a. Sort items by Date Modified
b. Open the latest log file using a notepad or other text editors.
c. Scroll down to the bottom
d. Examine the latest log
5. Analyze error messages found from Step 2, 3 and 4.
6. Investigate issue for 10 minutes
a. Examine the system account used for an application pool of a SharePoint application. Does the account have proper permissions?
7. If you’re stuck for more than 10 minutes, stop what you’re doing.
8. Search for the clues from Internet — Many times, we forget how useful Internet is and that somebody else typically had the same problem before.
9. If no clues have been found, ask for help.
a. Describe detailed steps how to reproduce the issues
b. Ask colleagues or reach out communities such as the MSDN SharePoint Forums 
10. Iterate the step 1 to step 5 until an issue is resolved.