Ignore the old adage that when taking portraits, the photographer should have the sun at his or her back. That just gives you washed out faces of people squinting. Count to three then take the picture on five or six, after the fake smile has gone. Or try taking two pictures in a row, one of the fake smile, the second of the genuine one that usually follows. It's easy to avoid that frustration by keeping a camera handy.
Spontaneous moments make priceless pictures.
To capture them, you need a camera with you. Getting close eliminates distracting, unnecessary backgrounds and shows the subject clearly. Think about showing just enough of the scene to make the picture clear and interesting. Be sure to check your camera manual to learn the closest distance at which your camera takes sharp pictures. Your pictures will have a feeling of lively spontaneity.