We usually take notes if we are not able to store all the information heard from the boss.
Some people take the notes and forget to concentrate what actually boss was needed. Some people concentrate and forget to note the steps that need to be followed. Any how now which is best?

I think both are important. First concentrate and then customize and take a note such that both will help to proceed your work with out any surprise or doubt. If possible make it as a diagram which will help more to understand at any time when you look back the same.