How to give power of attorney to my friend who is staying in another country (Canada). I am staying in India.
I assume that you mean "residing" rather than just "visiting". It depends on whose courts have jurisdiction. Let's say you have property in India, and you want a Canadian resident to be able to sell that property. The Powers of Attorney Act, 1882 (India) would be relevant to you (to avoid a complication, I assume you don't mean "in Jammu and Kashmir"). Clause 2 says that
The donee of a power-of-attorney may, if he thinks fit, execute or do any instrument or thing in and with his own name and signature, and his own seal, where sealing is required, by the authority of the donor of the power; and every instrument and thing so executed and done, shall be as effectual in law as if it had been executed or done by the donee of the power in the name, and with the signature and seal, of the donor thereof.
Per clause 4, you may (not "must") deposit this
in the High Court or District Court within the local limits of whose jurisdiction the instrument may be.
There are many kinds of POAs recognized by Indian courts, and you would be advised to consult an attorney familiar with Indian law to write up the correct POA. FYI, this page explains a different scenario – how does an Indian living outside of India write and register a POA that will be effective in India?
However, this won't help if you have property in Canada which you want to sell. Let us say that the property is in BC so the BC courts have jurisdiction. The BC law is here. The main ideas are the same as in India, but the details of implementation differ. §13 describes the formalities for form, signing and witnessing of agreements in BC (you will need two witnesses).
BC courts have no jurisdiction over medical decisions to be made in India, therefore if your concern is over who will make decisions for you when you are medically incapacitated, then since you are in India, you have to please the Indian courts, not the Canadian courts. If you plan to sell real estate in India but for some reason don't want to do this yourself, you would still need to satisfy the requirements of the courts of India.