If you make art and it's halfway decent to look at, you're going to get some embarrassing praise. "I love your art. You're so talented." Soon after, you will be treated to tales of personal failure. "I have no talent. I can't draw a straight line (or my way out of a box.)" You might hear stories from the same people about how they loved to draw and paint and make things when they were little kids, and then someone ruined it for them. The someone was probably a perfectly well-meaning parent or teacher. Perhaps the art was compared unfavorably to some else's or was misunderstood. Perhaps the youths were rebuffed for using things not intended as art supplies. Or for wasting time.
I don't want to be that person who ruins art for someone else. What I want to do here, in fact, is to give my reader tools not to be that person either. I have taken plenty of art classes as a child and an adult from a wide range of instructors. I've weathered a lot of criticism of my work, some very valuable and some entirely unwelcome. I have done many hours of artwork along side many children of widely varying interest and capability. This is where I have collected my ideas. This is intended primarily for people speaking to children about their art, but I find it works with adults as well. It may also work for areas of human endeavor other than art.
Do not give unsolicited critiques or opinions. If someone shows you their work, you may assume they are soliciting your opinion. Never assume someone is seeking criticism or suggestions unless they explicitly ask.
When you give your opinion of a work of art, be sure that it is your opinion, and not a value judgement. Do not say it is "good" or "not good." If you like it, say so. Elaborate on what you like. "I love your colors. . . I admire your bold lines. . . Unicorns are my favorite things." You can talk about how it makes you feel, whether a picture feels peaceful or has a lot of energy.
Feel free to ask questions,
except "what is it supposed to be?" You can say, "Tell me about what you painted" or say, "it looks like buildings to me. Where is your scene taking place? Is it from your imagination or something you have seen? Who are the people and what are they doing? Does it express something you are feeling?" I think it's okay to ask, "How do you like it? Are you happy with it?"
Acknowledge effort. If it looks like someone is very skilled, acknowledge that it is clear they have put a lot of practice and effort into honing their abilities. Saying people are talented not only discounts the effort they have put into their art, but can be discouraging to others in the same space. Efforts in a particular piece of art might be speed or it might be the considerable amount of time that was put into it. You might note the looseness and freedom of the technique or the precision and detail.
Do not tell any artist, particularly a small child, that they have to sign their work, unless you are paying for it, or it is to be handed in to a teacher. Whether or not an artist signs a work is entirely up to them, and a signature is an element which they may or may not wish to add. It is like telling the artist to add clouds or the color red, which you also shouldn't do, unless the artist asks you, "what else do you think I should add?"
Discourage frustration and feelings of failure. You can quote Bob Ross, "There are no mistakes; only happy accidents." Discourage people from wadding up drawings and throwing them out. Point out that mistakes are part of practice, and practice is how you build skill. You may suggest they try to rework the rejected piece into something they are happier with. Or that they keep it for a while to see their progress and improvement.
Acknowledge choices. Creating at all is a choice. As is what you create - the size, shape, color, medium, composition, subject, abstraction. Every single element of a work of art is the artist's choice. If you tell a young artist, "I like how you grouped the bright colors and oriented the paper lengthwise," you are also letting them know that they have power and agency, at least in this place, and that their possibilities for creation are infinite.
This post is delightfully illustrated with pictures made for me by Ruby, Chris, Nayeen, Angie and Anonymous.