Is there a rule of thumb for balancing a boom on light stand?

After a shoot I noticed that one of my booms developed dents on the stem. With chinese quality I am not surprised- however I own a second chinese boom that handled the same weight.

Therefore, are there any recommended physics behind boom loading and length?

eg. 2/3rd of total length ahead of the fulcrum
1/3rd of the total length behind the fulcrum with weights?

Obviously this can be calculated accurately with some physics, however this question has to do with photographers and any existing rules of thumb that would make this quicker and safer work.