If you have a DSLR (or an film SLR) learn how to use it in manual. It's best to practice with, say, a piece of fruit or a doll that won't get tired of you.
Step 1: Take it off auto and learn to read the in-camera meter.
Otherwise, it's just a very expensive P&S. For white skin you want to expose about 1/3 to 2/3 of a stop over.
Which means, when you look in the view finder you'll see a grid thus:
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The one in the middle is "correct" exposure, but for close ups of white skin you actually want the slider a bit towards overexposure because us palefaces are paler than % of grey that the camera uses to determine "right".
Stick it on Manual and start changing the ISO, f/ and shutter speed settings.
ISO is how fast the film will record the picture. The higher the number, the faster the film. The lower the number, the crisper the picture will look. To start out with you want to use the lowest ISO you can.
f/ is how much of the background will be out of focus. The smaller the number, the less will be in focus but the more light the camera will let in. It's hard to hit focus with anything smaller than 4.0 when you are starting out.
Shutter speed is how long the camera lets in light. My hand is too shaky to handle anything below 1/125.
I usually set the SS to 1/125 or higher, adjust the f-stop to where I want it to be, then pick the ISO based on the in-camera meter, and finally fine-tune with the shutter speed.This shot
is all natural light indoors with an ISO of 3200.