Trying to solve problem for which I asked help in Looks like total number of parts and sum of them differs on bricklink I understood I did not have the skills to check contents of a set. I did Web search for "site:bricks.stackexchange.com how to check completeness of a bought set" and did not find relevant info so making new post. The question How to check the missing pieces of a given set? is titled similarly, but asks about different thing from mine.
Initially I tried to count parts by tens, put them in one place and keep count of tens. I miscounted set of 602 by about 10‰ of parts. Then I tried to go by bricklink list again keeping track in tens. Again I failed though twice less.
Finally I separated parts by each "type", taking large area on the floor and going by bricklink list I glanced at the parts, checked presence and added up. On that way I found several occasions where I misplaced parts, but finally I got exact count, so I bought complete set as expected. Picture of layout below:
What are your favorite ways to check completeness of bought sets?