Rule #1 of taking good pictures: have a camera
Seeing a perfect shot does you no good if you don't have the camera with you.
Rule #2: take a lot of pictures, and throw away all but the best.
An amateur will shoot a dozen frames and show all of them to everyone. A pro will shoot a hundred frames, and show only a few.
The thing that most often separates good pictures from amateur snapshots is not the subject or the pose, but instead the car, messy table, garbage can, or whatnot, in the background.