Doing your best is not good enough. You have to know "what to do", then do your best ?

I agree with the idea.   

However, I have some reservation regarding doing your "BEST".

Experience has taught me to NEVER do your best and keep a BUFFER somewhere for overachievement benefits

Let me give you an example

If you determine that you can do your best in a job and finish it in2 hours.

If you commit yourself to2 hours and you are one minute late, then you are a bad guy

If you ask for3 hours, and finish the job in2 and half hours, you are a hero !!

Let me give you another example

If you do your best in a job, and you excel in it, your best reward could be (your boss decision) to stick you to this job for ever and never get the chance to move forward !!

So, my advice and this is what I have done most of the time,  do your job to a very high standard, but keep some time and energy to invest in exploring your next career advancement steps and how to proceed and move forward !!

I agree and wish to add to "What to do", when to do and then how to do which leads to doing it finally. A purpose is important then road map and finally the efforts.

align your goal with organisation goal and put your best efforts

I agree to Mr. Tihab

90 % i agree with you

10 % if i dont know what exactly i have to do , i will do my best , and see if it was right start or not

Nodoubt, in the present time we have alot of best doers but very few are those who know what best to do. So, i prefer keeping myself as intellect in finding what to do first in the best way possible. 

Agree.

i agree,proper planning is key to success.

BIG TIME. This is an important perception of waste elimination and free quality boosting.

AGREED ,,, YOU HAVE TO DO WHAT IS NEEDED ,,,,