ok, here we go.
lighting is super duper important when you're taking photos. if you can get lighting down, you're pretty much golden. so, a couple of simple things...
if you're outside, make sure that the sun is behind you (shining on to your back) as you're taking the photo. the sun/light should shining on to your subject, not you. mid-day sun is the worst. it's too strong and easily casts shadows. i try to avoid taking photos at this time all-together. morning and late-day are great. sunrise and sunset are the ultimate because the light is golden.
hello, lovely golden sunset light.
cloudy skies are also great.
if you're inside, try to use available light (as opposed to a flash) if there's enough of it. move closer to a window (or a lamp) if you have to. flashes don't generally make for very nice photos. try not to use it if you don't have to. if there's not a lot of light, keep your subject and your camera very still. place the camera on a stable surface (like a table) if you can.
indoors. no flash. very still.
if you have to use your flash, try to be 10 feet or so away from your subject. otherwise, the subject ends up being too dark or overblown.
warm lighting is generally the most flattering. i adjust my point-and-shoot camera so the little cloud symbol is on, which means that the camera is adding more warmth to the shot. it's kind of my default. i change it if there's too much warmth but, as with most things in life, i generally prefer to have too much than not enough.
again, if you're using a flash, have your subject look slightly to the side of the camera to avoid red-eye.
you don't have to center your subject in every photo you shoot. decentering your subject is an easy way to jazz up a photo. imagine that there is a tic-tac-toe grid on your frame/photo, then place your subject at grid intersections.
decenter your subject!
placing the camera at your subject's eye level or higher should help avoid double-chin action. and generally makes them look slimmer than if it's below.
try to create a frame around your subject using the background. so if you're shooting someone who's standing in front of a bunch of trees, for example, have them move to the spot where they are perfectly framed by the trees. maybe that means that you have them stand in the spot where there is the same number of trees on either side of them. actively seek out nice-looking backgrounds. at the very least, just keep the background in mind and don't be shy about repositioning your subject. try to avoid clutter in the background.
if you're shooting people, give them positive feedback. tell them how awesome/hot/cute/gorgeous they look. you'll get a better shot out of someone who feels attractive than someone who feels uncomfortable.
take lots of photos. i once asked a photographer friend what his best advice was for taking better photos and this is what he said. the more photos you take, the more likely you are to get a great shot.
ok, i think that's all i've got.