Another question is:
if I want to keep adjacent stone level for next course to do 1 over 2 and then 2 over 1, I found it will make me build a relatively levelled course. Then I have to use the same or similar thickness stones. My wall is about 73' long. I am worry it will be hard to find similar thickness stone later. Should I always keep adjacent stone level? I know I can use very thick stone to change to a new thickness level but the final result is the same, I think.