How to give and take constructive criticism
This would be my no.1 point for several reasons. Constructive criticism is an oximoron. Constructive in that you want to make a positive change, improve or build up, and criticism, to pull down, remove or otherwise negate a negative. So, with that in mind, how could you take criticism (a -ive) and be constructive (a +ive)? You have to consider YOUR motivation. Do you REALLY care about the person, and their wellbeing? Or do you just want to make your opinion heard?
We all have ideas and opinions, which we hold to be good, valid and useful. They "may be" the right thing to say. You MAY BE 100% right, but that does not give you the right to "push" that on another. Just calling it a "consrtuctive" criticism, may be nothing more than a thin desguise for putting others down. (Often to lift yourself up)! This happens all to often, people put others down, just to make themselves look good, or superior in some way.
Think, before you say anything. Even ponder/meditate on your words and delivery before you open your mouth. It could even be the wrong time and the wrong place. Check your motives! Someone once said "engage brain before opening mouth."
Ask permission to say anything that could be taken the wrong way, from the person. "Pardon me, but do you mind if I point something out to you about that (. . xyz. . .)?" Though you may have a valid reason to "help" the other person, they may not want it (right now). This could have been obtained previously. You may have a good relationship with the other person, and you may have at some point agreed, that if something needs to be said, or pointed out, you are free to do so.
An example may be a wife saying to her husband, "If you catch me about to say or do (. . xyz . .) please stop me, before I do (again)."
Or the husband .."If I start picking my nose/scratching my butt (or whatever else), point that out to me".
Or just say to a friend, "hey, you have my permission to correct me if you feel I'm being/saying things that are hurtful, etc."
We don't want to be caught out doing dumb, stupid things. None of us want to be put down or disrespected. We all know that we can (and do) do and say stupid things. Things we later regret. Having these "mistakes" pointed out in the wrong way, wrong time, wrong attitude etc, will only produce a reaction, and NOT a positive change.
The test of a true friend is one who can be trusted to have your best interest at heart. Once this is defined or established, we can feel secure in the knowledge that criticism given is for our own good. (Even if it sounds hurtful/painful at the time.) These kinds of friends are not always easy to find. It takes time and effort to build this kind of friendship, but WOW, when you have that, you have a real treasure. Don't loose it
Dont abuse it. Use (constructive) criticism sparingly, and with the right motivation.
As to receiving the same, just put yourself in that position, and receive it with the right motive. Don't be threatened by it, but take it and make the neccessary changes. You will be better for it. Change takes effort and work, otherwise you will stay the same. All the best as you grow!