A few months ago, a group of cardiac patients was divided into three groups – 
a) The first group was informed that some people are praying to God for their successful surgery, 
b)The second group was not informed that someone is praying for their recovery, but in fact, a group was praying for them, and 
c) Nobody was praying for the third group. The purpose of this study was to ascertain whether God does respond to prayers or not.
What was the outcome? 
The group, for which no one prayed had the most success, next was the group which was prayed for. but the patients were unaware of the fact. and the group which was informed that people were praying for them came last. Understandably, religionists were up in arms against these studies, because they argued that materialistic science and technology should be aware of the limitations of their abilities. And not venture into realms which are beyond their grasp. 
Obviously, this result would throw into dispute the validity of prayer. Is there a God who listens to our prayers? How much to pray? What are the right kinds of prayers? Is prayer a lever or handle to manipulate God into fulfilling our demands? 
The Oxford dictionary defines prayer as – "A solemn request to God or an object of worship; a supplication, thanksgiving, or other verbal or mental act addressed to God."  This definition thus makes it clear that a person makes a request knowing his inability to achieve the desired objective. If God fulfills them then He is seen as a "good" God. 
The Vedas deal with rhree departments of acrivities. One is called karma-kanda activities under Vedic injunction, which gradually purify one to understand his real position; the next is jnana-kanda, the process of understanding the Absolute Truth by speculative methods; and the third is Upasana-kanda, or worship of the Supreme Personaliry of Godhead and sometimes of the demigods also. The worship of the demigods recommended in the Vedas is ordered with the understanding of the demigods' relationship to the Personality of Godhead. 
In animal life there is no scope for prayer. They just live their lifespan in a mechanical way. In human society, even amongst the aborigines and primitive peoples there is some sense of accepting the superiority of nature. Therefore these societies are found to be praying to some great tree or mountain. And the followers of the karma – kanda ,jnana-kanda and Upasana-kanda follow their own rituals and worship. However, a glaring discrepancy in modern society is that most people do not follow any of the three processes and at the same time do not think about themselves as aborigines or primitives, still, expect God to fulfill their demands. 
Srila Prabhupada declares the following prayer by Lord Cairanya Mahaprabhu to be the ideal prayer – 
ayi nanda-tanuja kinkaram 
patitam mam visame bhavambudhau 
krpaya tava pada-pankaja sthita- dhuli-sadrsam vicintaya 
[Siksatakam 5] 
"0 son of Maharaja anda, I am Your erernal servitor, and although I am so, somehow or other I have fallen in the ocean of birth and death. Please, therefore, pick me up from this ocean of death and fix me as one of the atoms at Your lotus feel" 
This should be the standard of prayer; we should only want to be placed as one of the atoms at Krsna's lotus feet to render service unto Him. Everyone is praying to God with some interest, but even if we pray to God, "Give me some money, give me some relief, a nice house, a nice wife, or nice food," that is also good. Yet this is not to the standard of Lord Caitanya Mahaprabhu's prayer. Our only prayer should be thar the Lord enables us ro serve Him birth after birth. Our prayer should be, "Dear Lord, You are so great that I want to engage in Your service. I have been serving all these rascals, and I am not satisfied. Now I have come to You. Please engage me in Your service." This is the last word in prayer. Some people complain that when they pray ro God they do not feel His presence. We should know that this is due to our incapacities, not God's. There are two conceptions of presence-the physical conception and the vibration conception. The physical conception is temporary, whereas the vibration conception is eternal.When we enjoy or relish the vibration of Krsna's teachings in Bhagavad-gita, or when we chant Hare Krsna. we should know that by those vibrations He is immediately present. He is absolute, and because of this, His vibration is just as important as His physical presence. When we feel separation from Krsna or the spiritual master, we should just try to remember their words of instructions, and we will no longer feel that separation. Such association with Krsna and the spiritual master should be association by vibration, not physical presence. That is real association. We put so much stress on seeing, bur when Krsna was present on this earth, so many people saw Him and did not realize that He is God; so what is the advantage of seeing? By seeing Krsna, we will not understand Him, but by listening carefully to His teachings, we can come to the platform of understanding. We can touch Krsna immediately by sound vibration; therefore we should give more stress to the sound vibration of Krsna and of the spiritual master- then we'll feel happy and won't feel separation.
(Syamananda Das)