Can't Connect To My Router With My Ipod Touch

When I try to connect to my router using my iPod touch I put the password in on my iPod and get the error message "unable to join the network".
I visited several iPod touch forums but I can't find any help, everything is so confusing.
What should I do to make it work?

It might be your router. Is it a Linksys router? Many people have issues with the iPod touch and the Linksys brand. To solve the issue, make sure you have the latest firmware of your router.

Have you typed in your password correctly? Check if your caps are activated.

If you still have the problem, go into Settings > Wi-Fi and tap on your network. Have you been assigned an IP? DNS?

Try restarting your router.
Also, if MAC address filtering is turned on it will prevent you from joining the network.

This may sound dumb but try entering your password in CAPITALS and see if it works.

It worked for my sister.