Photos are so diverse that no one has a specific formula for the "best" photo. Also, many people have different styles, and customers have different likes and preferences. However, there are a few key elements that can be used to create a beautiful photo in many different styles and settings.
Having cohesive colors in a photo will almost always produce a more appealing picture overall. There are a few ways to incorporate cohesive colors into your next shot. If you are shooting photos of multiple people, matching or coordinating outfits will always help. This will allow for easier editing, and it will give your photo that little extra beauty that is overlooked sometimes. It is completely possible to create a stunning photo with non-matching outfits, but having your clients coordinate their clothing will take your photo to the next level. The next way that you can create a cohesive color scheme in your photos is to pick a location that has matching colors for the background. A great example of this is urban style photos in a city with tall buildings. Many of the buildings will either be the same color or colors that blend well with each other. This allows the photo to have a certain aesthetic that arises from the background because of the blend of colors. Finally, there is an obvious way to have color cohesive photos. Coordinate the outfits with the location. It sounds simple, but a photo is more appealing to the eye if everything matches in some way. Sometimes, photographers edit to achieve this effect instead of planning ahead for it. That is totally ok. Honestly, that is another way to have color cohesive photos. Finding your specific style and edit can ultimately produce photos that are very appealing due to the color palette of the edit.
In my experience, I have noticed that sometimes the angle of the photo can literally be everything. We have all opened our front cameras on our cell phones and had a slight embarrassed panic attack over the fear of looking like "that" in real life. However, when we angle the camera up to a normal level, we see that it was simply that... the angle. Now, apply that same logic to taking photos with a professional camera. It's always easy to spot a beginner photographer because of the angles of the photos. I am not trying to hate on beginners because the knowledge of which angle works and which angle doesn't work comes from experience. We all had to experience those times and learn form them. Frankly, we are all still learning. I believe that we should never stop learning, and this applies to angles in photography as much as it does to anything else. A very simple turn of your body or up and down motion of the camera can completely change the overall feel of the image and ultimately create a more beautiful photo that stands out.
This only applies to photos of people, but it can make or break a photo in certain situations. Have you ever seen a photo of someone that just looked awkward? The photo may have been beautiful in the areas of cohesive color and interesting angles, but the emotion coming from the subject just seemed out of place. That's probably because it WAS out of place. True emotion from a subject in a photo is something that I always strive to achieve. It's not always easy, but it is always something to search for. The emotion of the person is what will shine through the most in a portrait session. That's literally what portrait sessions are for. So, if you can pull out the real personality of that subject then you have already created a more beautiful photo. People want to see and feel the real emotion. Sometimes, that boring old pose and that fake "I have to grin for the camera" smile just does not cut it. Think outside the box when posing your subject. Get to know them as a person in order to figure out what they will respond naturally to during a session. Be an inviting person to make them feel comfortable enough to show you who they truly are. The end result is a photo with real emotion pouring out of it. That will be a truly beautiful photo.