Two decades before Jesus's birth, a prophet named Nephi preached the gospel of Christ and the coming of the Messiah on the American continent. The people among whom he labored were proud and stubborn. Few of them accepted Nephi's words. Nevertheless, he worked diligently and fearlessly for years to bring the people to repentance.
At a particularly low point in his ministry, not knowing what more he could do to bring righteousness to a benighted population, Nephi heard the voice of God. The Lord encouraged Nephi to continue his efforts and gave him this blessing and promise:
And now, because thou hast done this with such unwearyingness, behold, I will bless thee forever; and I will make thee mighty in word and in deed, in faith and in works; yea, even that all things shall be done unto thee according to thy word, for thou shalt not ask that which is contrary to my will.
The most powerful prayers are those that align with God's will. Though I am certainly no prophet, when I learn to pray for what God wants, and I want the same thing in all sincerity, He is unrestrained in granting my petition. The key to getting what I want is to want the right thing, which is the thing God wants for me. So, a good start to a powerful prayer is to ask, "Lord, what do you want for me?" When I get that answer, the rest falls into place.