Q: I have lost my iPhone how do I report it?

Call the local law enforcement.

http://support.apple.com/kb/HT2526

Tells you how to get your serial number. If the police find your device that can be used to ID it and get it back to you.

Apple really does nothing with stolen devices. 

What you need to do is protect your data. Change passwords for any accounts that were accessed on that device, notify any financial institutions that you accessed on the device.

If you have the 'find my iphone/ipad' app you can see if you can see where it is. but the app doesn't do too much because your device must be on the internet and a knowledable thief can defeat the app in a matter of minutes if they know what they're doing.

You posted in the iPad forum instead of the iPhone forum. To get answers to your question, next time post in the proper forum. See https://discussions.apple.com/index.jspa  I'll request that Apple relocate your post.

Here's some related info on iPads.

Apple (and no one else) can not assist (with serial number or iCloud) in finding a lost or stolen iPad.

Report to police along with serial number. Change all your passwords.

These links may be helpful.

How to Track and Report Stolen iPad

http://www.ipadastic.com/tutorials/how-to-track-and-report-stolen-ipad

Reporting a lost or stolen Apple product

http://support.apple.com/kb/ht2526

What to do if your iOS device is lost or stolen

http://support.apple.com/kb/HT5668

iCloud: Locate your device on a map

http://support.apple.com/kb/PH2698

Report Stolen iPad Tips and iPad Theft Prevention

http://www.stolen-property.com/report-stolen-ipad.php

How to recover a lost or stolen iPad

http://ipadhelp.com/ipad-help/how-to-recover-a-lost-or-stolen-ipad/

How to Find a Stolen iPad

http://www.ehow.com/how_7586429_stolen-ipad.html

What NOT to do if your iPhone or iPad is lost or stolen

http://www.tomahaiku.com/what-not-to-do-if-your-iphone-or-ipad-lost-or-stolen/

Apple Product Lost or Stolen

http://sites.google.com/site/appleclubfhs/support/advice-and-articles/lost-or-st olen

Oops! iForgot My New iPad On the Plane; Now What?

http://online.wsj.com/article/SB10001424052702303459004577362194012634000.html

If you don't know your lost/stolen iPad's serial number, use the instructions below. The S/N is also on the iPad's box.

How to Find Your iPad Serial Number

http://www.ipadastic.com/tutorials/how-to-find-your-ipad-serial-number

iOS: How to find the serial number, IMEI, MEID, CDN, and ICCID number

http://support.apple.com/kb/HT4061

 Cheers, Tom