Look at iOS Troubleshooting Wi-Fi networks and connections http://support.apple.com/kb/TS1398
iPad: Issues connecting to Wi-Fi networks
http://support.apple.com/kb/ts3304
iOS: Recommended settings for Wi-Fi routers and access points
http://support.apple.com/kb/HT4199
Additional things to try.
Try this first. Turn Off your iPad. Then turn Off (disconnect power cord) the wireless router & then back On. Now boot your iPad. Hopefully it will see the WiFi.
Change the channel on your wireless router. Instructions at http://macintoshhowto.com/advanced/how-to-get-a-good-range-on-your-wireless-netw ork.html
How to Quickly Fix iPad 3 Wi-Fi Reception Problems
http://osxdaily.com/2012/03/21/fix-new-ipad-3-wi-fi-reception-problems/
If none of the above suggestions work, look at this link.
iPad Wi-Fi Problems: Comprehensive List of Fixes
http://appletoolbox.com/2010/04/ipad-wi-fi-problems-comprehensive-list-of-fixes/
Fix iPad Wifi Connection and Signal Issues
http://www.youtube.com/watch?v=uwWtIG5jUxE
You can download a complete iPad User Guide here: http://manuals.info.apple.com/en/ipad_user_guide.pdf
Also, Good Instructions http://www.tcgeeks.com/how-to-use-ipad-2/
Apple - iPad - Guided Tours
http://www.apple.com/ipad/videos/
Watch the videos see all the amazing iPad apps in action. Learn how to use FaceTime, Mail, Safari, Videos, Maps, iBooks, App Store, and more.
iPad How-Tos
http://ipod.about.com/lr/ipad_how-tos/903396/1/
You can download this guide to your iPad.
iPad User Guide for iOS 5
http://itunes.apple.com/us/book/ipad-user-guide-for-ios-5/id470308101?mt=11
Cheers, Tom 😉