You might want to download Commview. After doing so, open up the program and select the Network tab. Make sure you also have your network card selected. A list of available networks will show up, along with their security type. Now, what you want to do is add that network into commview.
It will give you an IP. You want to add that IP into the Sniffer Tab. Next, it will ask you for a username and password. Now, usually, people are lazy fucks who won't bother changing the default username/password, so try
Commview should lag like shit at this point, and you should be logged in. Look around the wireless tabs and there should be some shit like HEX password. Click on it and change it to text and there's your wifi password. This won't always work, but 90% of the time it will.
And by changing it to text, there is not an option you can do in commview. What you have to do is manually decrypt the hex value and change it to text. Google hex to text and it should give you some links in which will make your life easier.
Once you have access to your neighbors wifi, you basically have access to all their information via commview. You can also use another packet sniffing program such as cain and abel or wireshark if you dislike commview because it is too hard to use. If you need any other help, let me know.