Use the light you already have
Most dull phone photos are not the phone's fault. They are the light's fault. Before you touch a single setting, look at where the light is coming from.
Window light is free studio light
Stand your subject a step or two from a large window and turn them slightly toward it. The side facing the glass goes bright and soft; the far side slips gently into shadow. That gradient from light to dark is what makes a face or an object look round and real instead of flat.
Turn the subject away from the window and the shadows deepen, which can look moody. Turn them to face it straight on and the light flattens. Rotate slowly and watch the shadows move — you are "aiming" the light just by turning the person.
Open shade saves the middle of the day
Direct noon sun gives squinting eyes and a hard black shadow under the nose. The fix is not a setting, it is a step sideways. Move your subject into the shade of a building, a wall, or a tree, while keeping open bright sky in front of them. The light becomes even and skin tones stay clean.
The hour before sunset does the work for you
As the sun drops low the light turns warm and comes in from the side, wrapping around things and stretching out long soft shadows. Almost anything photographed in that last hour looks better than it does at noon. If you can choose when to shoot, choose then.
Avoid mixed light when you can
Indoors at night you often have a warm lamp on one side and a cool screen or window on the other. The two colours fight and skin ends up an odd shade. Try to light your subject with one dominant source — turn off the competing light, or move closer to the one you like.
One thing to try today
Photograph the same cup of coffee twice: once under the ceiling light, once beside a window. Put them side by side. The difference is the whole lesson.