With the grid up, try placing your subjects along those lines or at the points where the lines intersect. It will make the photos much more interesting than being smack dab in the middle of your frame.
You can do this with subjects like lighthouses, people, flowers and everything else. But it's also a good idea to do this with your horizon lines, too, so that your horizon never cuts through the center of your frame.
Once you get into the habit of following the rule of thirds, you'll start to have a better sense of a photo's balance. When you're at the stage where you think you're getting the hang of it, start breaking the rule and see what works and what doesn't.
3. Learn how to see light
If you're going to go out and make pictures that impress your friends, you're going to need good light. What is good light, exactly?
Good light is the kind of light that gives a scene shape, depth and makes things look interesting. Generally, shooting indoors with artificial light or outdoors midday or with overcast skies is bad, flat and boring light. You'll know flat light when you see it - there are few shadows, if any, and everything looks evenly lit.
Look for light with some kind of direction and color. This type of light happens naturally at just before sunrise and at sunset. Alternatively, window light is great because it has direction and it's often soft and a little diffuse, so it's not harsh on your subjects.
Good light is especially important in mobile photography because you can't create much more interest with different focal lengths and varying depth of field. You're stuck with one focal length, and one aperture setting. It's a very good exercise in shooting light and finding good composition.
4. Find an interesting moment
Say you're at a beautiful location, the light is gorgeous and everything is ripe for a great photo. But nothing's happening. It's like looking through your Instagram or Facebook feed: there are hundreds of sunset photos with nothing but just sunsets. That's it.
Instead, find something to complement the scene if you can. Maybe it's just someone walking by. Wait until the shape of the walking person balances the photo and is at peak action, then snap away.
Sometimes, there are no moments. Nothing is happening. There's no one around, and it's just a pretty scene. It won't hurt to take the photo. Do that and keep it for yourself or share it with close people and tell a story along with it.
But if you really want to get the good stuff, find a good moment. Maybe it's people peacefully relaxing in the park - sleeping, eating, chatting, reading. Or maybe it's a quarrel on the street (just be safe). Keep your eyes open for movement and always try to find some way to balance the photo compositionally.
Without moments, you're probably just shooting still life most of the time. It's too easy, and we can all agree that there are more than enough food photos on Facebook, Twitter and Instagram these days.
5. Work the scene
What does it mean when a photographer tells you to work the scene? It means almost that - work it! Don't just stand there, compose and snap one photo and move along. Maybe a better shot will come along in a minute, or in five minutes.
Or perhaps you'd get a better photo of your subject by standing closer, or further away. Maybe the photo would look better from a lower angle, or a higher one. Or you can compose the same scene in a different way, or three different ways.