Trouble Shooting server problems

Loss of connectivity:
Check all cable connections.
Check media state for all wired and wireless network interfaces.
Check network connectivity by pinging another computer on the network.
Check internetwork connectivity by pinging a com
Check IP address and default gateway settings.
Check DNS and WINS
Check proxy settings.
Check security policies and authentication settings.
Check whether the server’s TCP/IP settings are correct

Physical layer problems:
Is the server running?
Are necessary peripherals attached and running properly?
Are network cables properly connected?
Are NICs connectivity/power lights on?
Is recently added hardware compatible with operating system?
Are correct drivers installed on server?
Are New Devices causing internel BIOS conflicts on server?

Name resolution problems:
Can you ping another system by both name and IP address?
Check DNS settings.
Check WINS settings.
Check HOSTS and LMHOSTS files.
Ensure that there are no obsolete host file entries.

Application Problems:
Does the application interact with networking?
Are all installed applications compatible with the configured network settings?
Check the event log for application errors.
Check the application log (Start Programs Admin.Tools Event Viewer) for application errors.

Print server problems:
Is the printing device working and are all connections secure?
Make sure the correct printer drivers are installed.
Check the print spooler service to ensure that it is running.
Check to see that there is plenty of disk space on the server for spooling.
Check the permissions set on the printer.
If your network is an Active Directory Domain,Check group policy settings for printers.

E-Mail server problems:
Ensure that the Mail Exchange (MX) resource records in your DNS entries are correct.
Ensure that the mail server has plenty of disk space for user mailboxes.
If you want your mail server to receive mail from other mail servers,ensure that your mail server is configured to enable relay.

Terminal Services problems:
In an Active Directory domain,check Group policy and individual users account properties if users are unable to connect to the terminal server or are unexpectedly disconnected.
Ensure that Terminal Services and/or Remote Desktop are configured correctly.
Ensure that you have set up a Terminal services license server and that you have sufficient licenses.

Dial-up/remote access server problems:
Ensure that remote access service are installed and configured on your server.
Make sure the service is started.
Ensure that your dial-in, PPTP, and/or L2TP ports are enabled to accept inbound remote access calls.
Ensure that the remote access server is configured to allow connections on the protocol(s) that are being used by the remote clients.

What else could the problem be?
Check your server's security settings,as well as any site- ordomine-wide security policies that may be preventing connectivity.
Check client licenses and licensing settings.
Check the routers and the client computers to ensure that the real problem doesn't lie elsewhere.