Firstly, make sure you have a USB Port 2.0- you probably will. (Try a different USB slot on your computer- this worked with mine)
The latest update of iTunes?
Mac OS X version 10.5.8 or later
Windows XP Home or Professional with Service Pack 3 or later
Make sure you have waited for at least 10 minutes with the iPad plugged in. If the battery is very low, it may take a while.
If this doesn't work, hold down the home and sleep button until the apple logo appears.
If nothing appears still, try holding down the home and sleep button for ten seconds. Then, let go of the sleep button but continue holding the home button.
If it STILL doesn't work, try restarting your computer. You could also try using another computer.
Some third-party software (such as security software, anti-virus software, and webcam drivers) may prevent iTunes from recognizing your iPad. You may have to update your software, adjust software settings, or temporarily disable the software.
If NOTHING WILL WORK, the only thing I can think of is to go to a nearby Apple Retail store or call a Mac Expert (this can be arranged on the apple website.)
Hope this helps! :)
(by the way, iTunes is good for all apple portable devices)