I've been asked a few times now about what camera I use. I always think that's a bit of a funny question. Yes, I do use a DSLR (Canon Rebel t3i) and that's probably of significance, but the actual camera itself is a lot less significant than the settings I choose and the lens that I use. Couldn't have planned that rhyme if I tried. So while I'm not a photographer, I thought it might be worth running through some of the most basic settings to think about and what the advantages of certain lenses are. Turn that camera to manual!
The aperture essentially determines how much light is let into your photo. The lower the f-stop the more light you have coming in. However, it becomes slightly more complicated in that the more light you're letting in, the smaller your depth of field. In other words if you have your f-stop set low, you're going to have a blurry background. If you have your f-stop set high, you're going to have more of your background in focus.
Having a soft blurry background tends to be a desirable trait in beauty photography so what you likely want to look for in a lens is one where the f-stop can be set quite low (this pretty much rules out your kit lens). I use the Canon EF 50mm f/1.8 lens because it's cheap as chips as far as lenses go and it gives that desired soft focus effect. However, if I had a little more to spend, I'd probably go for a lens like the Sigma 30mm f/1.4, which would allow me to shoot closer to the subject, while letting even more light in and creating a greater soft focus effect.
|Taken with an F-stop of 1.8: brighter with a blurred background|
|Taken with an F-stop of 6.3: darker with a less blurred background|
Shutter speed is the amount of time your camera shutter is open for when you're snapping a shot. It's another factor that determines how much light you have in your photo. If your shutter speed is slower, more light is going to be let into the photo. Seems good. However, if you go too low you're more likely to end up with a shaky, blurry photo. For a still shot I generally try not to go below 200.
ISO determines how sensitive your camera is to light. If you don't have a lot of natural light where you're shooting and your ISO is set low, your photo is going to turn out quite dark. Turning your ISO up is a beauty photographers best friend. However, and of course there's a however, turning your ISO up too high will result in a grainy effect to the photo. So ideally you really want to have a decent light source wherever you're shooting. I don't ever really turn my ISO above 800, maybe 1600.
|Taken with an ISO of 400 and studio lights: minimal grain|
Low f-stop = more light, blurry background
Low shutter speed = more light, shakier photographs
High ISO = more light, more grain
When it comes to photography everything is about balance. There are advantages and disadvantages to every setting and even every lens. One thing I didn't really touch on here was focal lengths. For a wonderful detailed post, with lots of visuals check out All About Prime Lenses & Focal Lengths on A Beautiful Mess.