Relax. Taking pictures of yourself is far less stressful than modeling for someone else. If you take a bunch of bad photos, you can just delete them off your digital camera before anyone else can see.
Do like models and actors do: practice some poses in the mirror first to see what you like and what is easy to do. The most important thing to show off is your smile. Maybe you like your mouth closed when you smile, or maybe you like to show all your teeth. Either way is fine: just remember whatever you do does not have to look perfect. It just needs to appeal to you, and it's okay!
It helps to push your tongue against the back of your teeth before smiling.
Take a photo a day. Take a photo every day, when you feel most comfortable about how you look. Your best time may be the morning, or in the evening—or whenever you feel how you want to project yourself. Confidence counts.
Put on some makeup if you like, do your hair a bit,or just anything that will make you feel better about yourself. If you take a bunch of photos on a low-self-esteem day, no matter how they really look, you'll probably find faults in them, only because you feel you don't look good that day.
Experiment with settings. A flash can really wash you out, which can be a blessing if you have lots of blemishes, but just know that people aren't stupid and if you've made the picture so bright that half of your face isn't showing or is blurry, they'll know something's up.
You can also set the camera to have different tints depending on the light. There is one setting, which is usually indicated by a little light bulb—indicating you're shooting in incandescent light—and this generally makes everything tinted blue if you don’t use the flash. Just play around with all the different options on your camera and see which one makes you look the best.
Using Instagram for your shot can give you instant access to some really "arty" photos of yourself that can turn a humdrum picture into something really interesting.