Hi Bharat C P,
You may want to take a look at the exam topics for the IUWNE exam (640-721 OR 640-722) and utilize the study resources and practice/review questions found here in the Cisco Learning Network. You may also want to try the Self-Assessment that is available for Wireless.
Please note that the last day to test for the current version of the 640-721 IUWNE exam is May 11, 2012. However, the new version 640-722 is now available.
In addition, you can look into Cisco Press self-study materials or perhaps taking a training course with a Cisco Learning Partner if your time permits. To find a Cisco Learning Partner, please visit http://www.cisco.com/web/go/class_locator
Best of luck to you on your CCNA Wireless pursuit.
Cisco Learning Network Moderator
I would personally wait for just a little bit to see if new updated study materials are released for the new CCNA Wireless exam that Rigo mentioned.
You could also join the CCNA Wireless study group here on CLN. There's a great group of people that all have expertise and will be more than willing to help.
First things first you need to have a valid CCNA to become CCNA Wireless certifed. Thats not to say you cant study, take and pass the exam you just wont be certified so if that is your goal make sure your CCNA is upto date.
Second the exams are changing in May I think and all of the available material is based on older technology and the old tests.
Hands on experience or labbing is the key to success in my opinion along with learning the theory and reading the documentation.
Look at the learning objectives and get familiar with them.