Rule of thirds
This is the classic rule that requires you to divide your frame into thirds and have a point of interest in one of the 4 intersecting points. It is believed that to the eye, this positioning of subjects in a frame looks appealing. As they say, rules are to be broken so don't be afraid to experiment.
I love to center it a lot of the time. I was trained as a graphic designer in art school so this is probably my bias to want to see symmetry in my work. Symmetry cleans things up a lot. It gives a sense of balance and orderliness. You can find your point of interest and just place it right in the middle of the frame. One trick is to have the main subject in the middle and let other subjects support it by telling a story about it.
Lines can be appealing to the eye if used in a frame. Find lines in nature, subjects. With lines, you can also work with interesting perspectives which make them even more interesting.
Textures are great to work with, especially if you fill the entire frame with them. You can experiment with these. It could be actual textures, patterns or just colors. One trick to make things even more appealing and interesting is to find something that breaks the monotony.
Space is a great way to have your subject stand out. You can experiment with using as much space as you can in a frame. There is an entire style of photography called minimalism.
There are frames in the environment around us that can be used to enhance our pictures. You can use vegetation to frame your shot so it’s not hanging, or you can find actual structural frames in architecture like arches.
Experiment with reflections on smooth surfaces. Those glass windows downtown when you go window shopping, the paddle of rainwater on the street after the rain, the top of a parked car
It is always said that if you don’t think your pictures are not good enough, it is probably because you are not close enough to your subject. Now I know this is an intimidating thing to do if you are a candid street photographer. It always feels like you might be invading people’s privacy and peace. Yes you really are but hey, you can always delete if things go south. On a serious note though, you will be surprised how much people want to be on camera. Take a few quick shots before they make eye contact and a few right after they do. Usually anything after that is unnatural. If you practice this, you will find your own sweet spot.
The horizontal line where the sky touches mother earth. Keep this as flat as you can. It is important to watch this line everytime you look through the viewfinder. One trick you can use to keep things normal and appealing is to have the horizon line in the center of your width. Have it divide the width of your frame in two. You can experiment with the horizon higher or lower than that of course.
Angles can be very interesting to work with. They give the viewer a different point of view. Try bird’s view from above, or a frog’s view from the ground. You can also tweek these angles by tilting the camera e.g when you have your camera above your head, you can either have it facing down or you can have it facing straight ahead like you would at eye level. You can also have the camera simply resting on the ground, or have it at ground level but tilted up. Remember, depending on what lens you’re using, these tilting motions will distort your subject.