Difference between до and к
  Looking back at some of my notes I am getting myself confused...
 
What is the difference between до + до  and под + к when used with motion verbs? I find it difficult to differentiate and my textbooks don't do a very good job.
 
For example, I think the following mean..
 
Я подошел к остановке. I walked up to the stop.
 
Я дошел до конца квартала. I walked (up) to the end of the block.
     Re: Difference between до and к
  I could try to explain it to you, but I would suggest that you do some independent research. Type all of the possible combinations of prefix + motion verb into google and see if you can understand the difference between the various combinations.  Even if you don't come to a full understanding, your knowledge of the language will improve immeasurably from this exercise.
     Re: Difference between до and к
  Yes, this can hardly be formalized. Any rule will not be absolute. Practice can not be substituted by rules.
 
Though... :)
 
"к"  is used when the ultimate destination of motion is referred to. 
"до"  is used when intermediate or unintended destination point is described.