Watch the lights
Since many of us are now using high speed connections to the Internet, we run into new problems. A customer of mine called me today and said she couldn't get email any more. When I asked if she was connected to the Internet, she thought she was. Knowing she had DSL, I asked how many lights were on the DSL modem (thingy from the phone company that connects the computer to the Internet with a cable running from phone line to it, and then another cable from it to the computer). She saw three lights on her particular modem, an Actiontec, which should have a minimum of four lights on it.
The solution: unplug the power from the modem for about fifteen or so seconds, plug it back in and wait for about a minute or so until the four (or five if wirelss is enabled) light up. We waited, she checked her email and presto, it worked.