For the Benefit of all, there is already a thread discussing this
http://www.pprune.org/archive/index.php/t-410108.html
What one needs to do is have a look at the forms
CheckList
The Main Form itself You only need to fill out COP23 out of this in case your case is that of a renewal
Annexure (For the 20 Year validity thing)
DD required is for Rs. 5000. Rest of the requirements are on the form, and they advise that one submits 3 months before the expiry as it takes that long to renew. This is the part I don't understand, why give an expiry date if they accept papers only upto 3 months before that.
Anyway, hope this helps someone.