In the context of the usage in Alma 5, "blame" is defined as:
responsibility for anything deserving of censure
"Censure" is defined as:
strong or vehement expression of disapproval
Thus, walking "blamelessly" before God means walking in such a way that God will not strongly or vehemently disapprove.
Two things struck me as I initially defined the central words and reached the defintion above - one which I have understood for a long time and one that was completely new to me.
The one I have understood for a long time deals with the nature of the Atonement and my understanding of the difference between "sin" and "transgression". Essentially, God does not disapprove strongly or vehemently of our best efforts to act according to the dictates of our own consciences. In fact, I believe our 2nd Article of Faith teaches that we will not be punished for the things we do as a direct result of the Fall - which, in this case, include transgressions of eternal law we commit out of ignorance or as a result of things we simply can't control. If we do not choose consciously to do things that are contrary to our best understanding of what we believe God wants of us, those actions are paid for through the Atonement of Jesus, the Christ - and I believe the magnitude of those things for which we have been redeemed already is MUCH larger than most people realize.
The second thing that struck me was not new in theory, as it is something I have believed for a long time, but it was new to me in the context of walking blamelessly before God. It really is just a re-statement of the first one I just explained, but I think it is important to phrase it the way it came to my mind. It is:
God does not expect us to walk "perfectly", nor does he expect us to walk without stumbling and falling and getting skinned up in the process. He simply asks us to avoid those things of which he would disapprove "strongly" or "vehemently".
The best example I can give is how I view my own desires for my children. I expect them to make mistakes in their lives. In fact, I believe that is the only way they will learn many important lessons in life - by experiencing the opposition that must needs be and failing occasionally (or more than occasionally, if they are like me). I am not about to react strongly or vehemently to the vast majority of mistakes they make. However, there are some things they might do to which I would react strongly or vehemently. Those things are so serious in my eyes that I would go outside my normal principle of teaching correct principles and watching them govern themselves to actively begging them to stop.
The thing that struck me is that there really are relatively few things that fit that category that I believe are "universally accepted", but, even with my own children, the underlying principle would be things that violate their own consciences. Thus, the things toward which I would react strongly or vehemently in relation to one child would differ somewhat from the things that would cause the same reaction in relation to another child - assuming I know my children well enough as differing individuals to understand what and how much they understand about the things they believe and the choices they make.
I can't "blame" them for things they do out of ignorance, and I refuse to "blame" them for things they do with which I disagree simply because I disagree - as long as I believe they are acting in accordance with their own understanding and conscience. Most importantly, the list of things they might do that would bring my strong and vehement disapproval and cause me to "blame" and "censure" them is much shorter than many people probably think.
What I gained this week from my contemplation of this concept of walking "blamelessly" before God is that the assignment of blame rests with GOD, not with us - and that, in my opinion, that assignment will be based MUCH more on how well we walk in accordance to the dictates of our own consciences than on the exact steps we take in our walk before God.