Philippians 4:19
Here are some of the ways he prayed. First, he never shared a need with anyone but God. Second, when he had a need, he opened his Bible, searched for a promise that fit that need, and then meditated on that scripture. Mueller believed in the power of thinking through scripture as much as he believed in the power of prayer. Third, he pleaded for that promise before God. And he didn't just pray for money: he prayed for individuals as well. Sometimes Mueller prayed for someone for as long as fifty years. He didn't stop praying for anyone or anything until he got his request. That's how convinced he was that God would answer his prayers. Through his prayers, Mueller obtained the modern-day equivalent of $150 M for his charities; he led tens if not hundreds of thousands to the Lord; and he lived to be 93 years old. That was the power of his faith and life. (link) 
"George Mueller was a native German (a Prussian). He was born in Kroppenstaedt on September 27, 1805 and lived almost the entire nineteenth century. He died March 10, 1898 at the age of 92. He saw the great awakening of 1859 which he said “led to the conversion of hundreds of thousands.”
1 He did follow up work for D. L. Moody,
2 preached for Charles Spurgeon,
3 and inspired the missionary faith of Hudson Taylor.
4He spent most of his life in Bristol, England and pastored the same church there for over sixty-six years—a kind of independent, premillennial,
5 Calvinistic
6 Baptist
7 church that celebrated the Lord's supper weekly
8 and admitted non-baptized people into membership.
9If this sounds unconventional, that would be accurate. He was a maverick not only in his church life but in almost all the areas of his life. But his eccentricities were almost all large-hearted and directed outward for the good of others. A. T. Pierson, who wrote the biography that Mueller's son-in-law endorsed as authoritative,
10 captured the focus of this big-hearted eccentricity when he said, George Mueller “devised large and liberal things for the Lord's cause.”
11In 1834 (when he was 28) he founded The Scripture Knowledge Institute for Home and Abroad,
12 because he was disillusioned with the post-millennialism, the liberalism, and the worldly strategies (like going into debt
13) of existing mission organizations.
14 Five branches of this Institute developed: 1) Schools for children and adults to teach Bible knowledge, 2) Bible distribution, 3) missionary support, 4) tract and book distribution, and 5) “to board, clothe and Scripturally educate
destitute children who have lost both parents by death.”
15The accomplishments of all five branches were significant,
16 but the one he was known for around the world in his own lifetime, and still today, was the orphan ministry. He built five large orphan houses and cared for 10,024 orphans in his life. When he started in 1834 there were accommodations for 3,600 orphans in all of England and twice that many children under eight were in prison.
17 One of the great effects of Mueller's ministry was to inspire others so that “fifty years after Mr. Mueller began his work, at least one hundred thousand orphans were cared for in England alone.”
18He did all this while he was preaching three times a week from 1830 to 1898, at least 10,000 times.
19 And when he turned 70 he fulfilled a life-long dream of missionary work for the next 17 years until he was 87. He traveled to 42 countries,
20 preaching on average of once a day,
21 and addressing some three million people.
22 He preached nine times here in Minneapolis in 1880 (nine years after the founding of Bethlehem Baptist Church).
From the end of his travels in 1892 (when he was 87) until his death in March of 1898 he preached in his church and worked for the Scripture Knowledge Institute. At age 92, not long before he died, he wrote, “I have been able, every day and all the day to work, and that with ease, as seventy years since.”
23 He led a prayer meeting at his church on the evening of Wednesday, March 9, 1898. The next day a cup of tea was taken to him at seven in the morning but no answer came to the knock on the door. He was found dead on the floor beside his bed.
24The funeral was held the following Monday in Bristol, where he had served for sixty-six years. “Tens of thousands of people reverently stood along the route of the simple procession; men left their workshops and offices, women left their elegant homes or humble kitchens, all seeking to pay a last token of respect.”
25 A thousand children gathered for a service at the Orphan House No. 3. They had now “for a second time lost a ‘father'.”
26He had read his Bible from end to end almost 200 times.
27 He had prayed in millions of dollars (in today's currency
28) for the Orphans and never asked anyone directly for money. He never took a salary in the last 68 years of his ministry, but trusted God to put in people's hearts to send him what he needed. He never took out a loan or went into debt.
29 And neither he nor the orphans were ever hungry. The eccentric pastor and orphan-lover was gone."
Continued
There is a ton of information on the web about George and a number of books about him and an autobiography. The
muller foundation is still around today.
To me one of the most inspiring things about George Muller was his faith in the midst of dire circumstances. Out of his four children, two were still born and another died at age one. He out lived his oldest child and was a widower twice, not to mention the deplorable conditions of the time. Yet he lived his life with amazing faith, depending on God to supply his every need.
