Pick an outfit that you are not entirely sure about to start. Not one that you feel awful wearing, and not one of your favorites. But something where you are unsure. Maybe the jacket is too long, maybe the pants are too heavy, or maybe the top is fine until you put on shoes. You want this type of outfit because then you have something to analyze: the silhouette. The silhouette is the outline shape of the whole outfit, before you start seeing any details. It includes shoulder shape, waist shape, hem shape, volume, and how the shoes are finishing the look. People new to styling might try to figure out the problem first in terms of color or trend, but silhouette shape is often a faster way to pinpoint what is going on. You can have two pieces that are the right color to be together but that still clash in silhouette shape. A loose top with a baggy pant can feel relaxed, or it can look undefined and shapeless, depending on where the fabric falls and where the silhouette is anchored.
The mirror gives you the ability to feel and see your outfit at the same time. Stand and see your outfit in a normal way, then also turn a little bit sideways. Sit down if your outfit is about a whole day. If not, you can just stand up. Does the waist shape disappear on you? Does the hem shape cut your leg off in an unusual spot? Does one layer look like it is adding more weight than you thought it would? Do not immediately try to fix every problem. Just describe the issue in simple, non-judgmental words.
Next, take a picture of your outfit straight on using natural light. A picture of your outfit is good for you, because a picture of your outfit is slightly flatter. A picture of your outfit has less movement and feeling, which is good because the shape is easier to see. Look for the main, basic shapes. Is the top shape larger or bigger than the bottom shape? Is the shoe shape giving more weight to the bottom of the look? Does the jacket shape end on a point where it adds extra bulk to the look? Is there contrast between shape and silhouette?
Then, change one thing and repeat the checking. Tuck your top in, or open your jacket, or wear a lower heel or a lighter shoe, or try a smaller jacket or coat. Take a new picture from the same angle. You have an easier time comparing two pictures, rather than trying to hold one picture of your outfit in your mind. You might find that one thing is making your waistline appear too big, or that a specific shoe was not the problem at all.
You may also find it useful to keep your notes very simple when doing outfit checks. Do not write that your outfit looks bad. Write what shape the top, bottom, or shoes are. “Your top appears too wide for these pants.” “A longer coat makes your legs look smaller.” “This flat shoe is more appealing for these pants than these boots.” “A v-neck works better with this jacket shape.” These simple notes give you some good advice. They also help you keep in mind when a piece that needs changing could be solved with an easier fix that just required a different layer or accessory.
The mirror tells you how the outfit feels on you. The photo shows you the basic silhouette balance. When both give you the same feedback, you have a great starting point to adjust your outfit. When the feedback does not agree, the most important feedback will be: is this outfit comfortable, and is it something you could wear for a particular reason, or something you would even wear?