Every photo I took of my desk plant that week looked flat and a little sad, no matter how many times I moved a lamp closer to it. My upstairs neighbor had a dog that barked through the ceiling most evenings that whole week, which is honestly most of what I remember about it now besides the plant.
Your first day
Starting takes twenty photos of one small object near a window with soft daylight, no flash. Nothing needs to be bought first, whatever camera or phone you already own is enough. Photograph it from directly above, from eye level, from below, and from close and far, moving yourself or the object but never touching the lights or curtains. Afterward, put your best and worst shots side by side and look at where the shadows fall.
Shooting with your back to the light source out of habit is the thing to avoid. It flattens everything and kills shadow detail. Turning the object, or yourself, so the light comes from the side produces far more depth than most beginners expect.
The thing most people miss
Two photos of the same plant, on the same phone in the same minute, taught me more than any camera review could: I took one from the exact same angle, lamp behind me, then turned it forty-five degrees so the window light hit the leaves from the side instead. The second photo had real shadow between the leaves. The first one looked like a sticker.
Once I stopped thinking about gear and started walking around a subject to find the light before raising the camera, the photos stopped looking flat.
What not to do
Don't shoot with the light directly behind you out of habit, even though it feels like the safe default. It's the single most common beginner mistake, and composition rules can't rescue a photo that never had any depth to begin with.
A shadow is what actually gives an object weight in a photo, not the object itself. Composition rules like the rule of thirds are worth learning once there's real depth already in the frame to arrange, not before.