Many router problems could be solved by going through following checklist:

• Check if your router is turned on. This could be easily done by looking if router is pluged in to the power socket and if there are any lights on it.
• Check if your computer has connection to the router. If your computer connected to the router via ethernet cable then you can check if there is a blinking light on a router next to the socket where the cable is plugged. If it is not then it is possible that cable is not working.
• Check if your router internet light is on or blinking (consult with manual to see what each state means)
• Make sure your router is connected to your cable/DSL modem. There should be either DSL or cable connection to the modem.
• Check if you can see router admin interface by typing http://192.168.1.1/ (replace it with your router IP address) in your browser address bar
• If you are using Wi-Fi connection to connect to your router make sure that your computer is connected to the wireless network managed by your router. You can perform quick and easy check to see if Wi-Fi network is managed by your router. To do it just turn router off and see which network disappears from wireless network list.
• Check if device that you're trying to connect to the router via Wi-Fi is not too far from the router. Certain building materials can significantly reduce transmission quality and make connection seem broken.