Q: iPad Charging for First Time

You did nothing wrong. You can use it out of the box without charging before hand.

Here's some battery/charging links that may be of interest.

The quickest way (and really the only way) to charge your iPad is with the included 10W or 12W (5W on Mini) USB Power Adapter. iPad will also charge, although more slowly, when attached to a computer with a high-power USB port (many recent Mac computers) or with an iPhone Power Adapter (5W). When attached to a computer via a standard USB port (2.5W, most PCs or older Mac computers) iPad will charge very slowly (but iPad indicates not charging). Make sure your computer is on while charging iPad via USB. If iPad is connected to a computer that’s turned off or is in sleep or standby mode, the iPad battery will continue to drain.

Apple recommends that once a month you let the iPad fully discharge & then recharge to 100%.

How to Calibrate Your Mac, iPhone, or iPad Battery

http://www.macblend.com/how-to-calibrate-your-mac-iphone-or-ipad-battery/

At this link http://www.tomshardware.com/reviews/galaxy-tab-android-tablet,3014-11.html , tests show that the iPad 2 battery (25 watt-hours) will charge to 90% in 3 hours 1 minute. It will charge to 100% in 4 hours 2 minutes. The new iPad has a larger capacity battery (42 watt-hours), so using the 10W charger will obviously take longer. If you are using your iPad while charging, it will take even longer. It's best to turn your new iPad OFF and charge over night. Also look at The iPad's charging challenge explained http://www.macworld.com/article/1150356/ipadcharging.html

Also, if you have a 3rd generation iPad, look at

Apple: iPad Battery Nothing to Get Charged Up About

http://allthingsd.com/20120327/apple-ipad-battery-nothing-to-get-charged-up-abou t/

Apple Explains New iPad's Continued Charging Beyond 100% Battery Level

http://www.macrumors.com/2012/03/27/apple-explains-new-ipads-continued-charging- beyond-100-battery-level/

New iPad Takes Much Longer to Charge Than iPad 2

http://www.iphonehacks.com/2012/03/new-ipad-takes-much-longer-to-charge-than-ipa d-2.html

Apple Batteries - iPad http://www.apple.com/batteries/ipad.html

iPhone: Hardware troubleshooting (Power/Battery section also applies to iPad)

http://support.apple.com/kb/TS2802

Extend iPad Battery Life (Look at pjl123 comment)

https://discussions.apple.com/thread/3921324?tstart=30

iOS 7 Battery Life Draining Too Fast? It’s Easy to Fix

http://osxdaily.com/2013/09/19/ios-7-battery-life-fix/

New iPad Slow to Recharge, Barely Charges During Use

http://www.pcworld.com/article/252326/new_ipad_slow_to_recharge_barely_charges_d uring_use.html

iPad: Charging the battery

http://support.apple.com/kb/HT4060

Best Practices for iPad Battery Charging

http://www.ilounge.com/index.php/articles/comments/best-practices-for-ipad-batte ry-charging/

Tips About Charging for New iPad 3

http://goodscool-electronics.blogspot.com/2012/04/tips-about-charging-for-new-ip ad-3.html

How to Save and Prolong the battery life of your new ipad

https://discussions.apple.com/thread/4480944?tstart=0

Prolong battery lifespan for iPad / iPad 2 / iPad 3: charging tips

http://thehowto.wikidot.com/prolong-battery-lifespan-for-ipad

iPhone, iPod, Using the iPad Charger

http://support.apple.com/kb/HT4327

Install and use Battery Doctor HD

http://itunes.apple.com/tw/app/battery-doctor-hd/id459702901?mt=8

To Extend a Device’s Battery Life, Get to Know It Better

http://tinyurl.com/b67c7xz

iPad Battery Replacement

http://www.apple.com/batteries/replacements.html

In rare instances when using the Camera Connection Kit, you may notice that iPad does not charge after using the Camera Connection Kit. Disconnecting and reconnecting the iPad from the charger will resolve this issue.

 Cheers, Tom

Let me simplify it so you don't have to spend 3 hours reading all those links...

You can and should charge as often and as long as possible... deep discharges are hard on lithium batteries.  Normal mobile use will result in the one charge cycle/month that Apple recommends.  Also, you cannot overcharge the device, thus you can leave it plugged in as long as you like.

Every once in a while, you may need to calibrate your battery meter if it shuts off before 1%.  To do this, fully discharge (until it shuts off) and then fully recharge (don't unplug until 100%) to recalibrate the battery meter.  You may need to do this a few times.

http://www.apple.com/batteries/iphone.html

That's pretty much all you need to know about your battery.