OK, I’m a professional photographer/photojournalist, so I can go on forever answering your question.
I don’t know what this L-composition or 3- 5- 7- shape stuff is. This doesn’t mean it doesn’t exist, I’ve just never heard it labeled as such.
The basic compositional rule you learn when you start is the “rule of thirds” or “the golden mean.” Now, let’s start by not calling it a rule, but a guideline. Basically, divide your frame into thirds horizontally and vertically. If you place your subject on any of the intersections of these lines or along one of these lines, the composition will be generally stronger than if you centered your subject.
“Never take pictures at noon.” Generally, this is true, but once again, there are exceptions. Noon light tends to be boring because of the angle, and because of the quality of light. Us photographer types love early morning and late evening light, when the angle it hits the face minimizes shadows, plus, because of the way it enters through the atmosphere, it takes on a golden quality.
Always have the sun behind you – Good general point, but does not always hold true. The basic thing you should learn is LOOK at what you’re taking a photo of. Look at the light. Look at the shadows. If you’re taking a shot of a building, sometimes it’s nice if the sun is off at an angle, so the light hits the facade obliquely and gives the building nice contours. In this case, the sun is not behind you. But the main point is observe. Your film is not going to make the picture better if the subject is in shadow. No matter what speed your using.
As Yeah said, illuminating people with a fill flash is much easier than having them stare into the sun. But another tip, if you want to make your flash photos look better, is to use a bounce card and/or take the damn flash off the camera (if you can) and hold it with your arms outstretched to the right or left, slightly above your subject. There is nothing more boring and ugly than direct flash. (unless you’re going for that Weegee look.)
And, one last compositional tip: Get in close. As Capa said, if you’re pictures aren’t good enough, you’re not close enough. Eliminate excess details in your frame. Get close to your subject.
If you have any more questions, feel free…