What was God the Father like, when he was a man? According to the LDS doctrine of exaltation, God the Father was born and lived and died, and then was exhalted to Godhood by his God, in the same way that Jesus was exalted by the Father. 

Is there any passage in the Mormon Scriptures or writing by Mormon teachers that discusses the life and character of the Father before he was exalted?
No, and in fact it is explicitly stated in LDS scriptures that such a revelation does not pertain to us:


  Moses 1: 35
  
  But only an account of this earth, and the inhabitants thereof,
  give I unto you. For behold, there are many worlds that have passed
  away by the word of my power. And there are many that now stand, and
  innumerable are they unto man; but all things are numbered unto me,
  for they are mine and I know them.


Any history of beings from other worlds and their experiences in mortality falls outside the scope of "only an account of this earth and the inhabitants thereof."