Giving criticism can sometimes be an expression of approval or strong disapproval, and at other times it can be a scrutiny. It is the critical assessment of a particular thing, or task as the case may be.
The average man is quick to give criticism, even though he/she may not have the ability to do half of what he is condemning or claims. So it is common to see people criticize but it is uncommon to see them criticize constructively, and this is why you are here.
I have written below six steps to take for your criticism to be constructive.

1. Giving criticism can be fun, and interesting, If done the right way, people would seek you to criticize them or their work. To give criticism you have to understand that no two people are the same, and as they are different, they are apt to make different choices, so mere understanding this important fact would help you
realize the people’s opinion should be respected, anything short of that is an insult.

2. Do not highlight the flaws, but appreciate highpoints: when giving criticism, do not pay attention to the mistakes; at least not yet, identify his/her strong points and dwell on that, if possible, compare with yourself, in areas you messed up (make sure you don’t use someone else as that might hurt his ego). When he/she is lost in cloud nine, then you do the next.

3. Subtly highlight the errors while making him feel good: To illustrate; Philip did poorly in a science test, but did well in math and average in English; do you jump at him for failing science? NO! If you praise him for doing math well, you’d boost his ego; tell him how many people failed science. If you ever failed science, let him know, also tell him how you felt. He should smile at this point (at least) then tell him, “if only you read more in science, you might have gotten what you got in English or even more; but I know you are working at it; its not easy , it never was, but your effort would pay off eventually”. Just praise him. if there are stats to support the fact that math students are good science students, share it with him, make him feel at ease he’ll decide by himself to improve & that way no one can stop him.

4. Don’t remind him of anything negative, but you are allowed to make reference to his previous success and achievements, this would arouse in him/her an interest to succeed even more than before.

5. Mean what ever you say: giving criticism constructively or the right way doesn’t mean you should be sarcastic. You are expected to mean what you say; no matter how often one takes or makes a wrong decision that does not make him anything less. Mean your nice words or like templar said “if you don’t have anything to say, shut up” (in templar’s word). Been sarcastic would be visible in your voice & actions. So make sure you keep it real.

Giving & receiving criticism are not the samething, to give criticism feels absolutely better, especially when done right, but it is a different kettle of fish to receive it, but just one advice for you when been at the receiving end of criticism especially when it hurts; realize that everybody has an opinion and people’s opinion of you is their opinion, not yours. You should not let anyone define you but you. Understand that there is no other you. Understanding this piece makes it less annoying especially when it is “destructive criticism”.
Do you criticize often, are you criticized often, what do you think about giving criticism

source Biscoibitade.com