If it were me, I'd take some photos at the location before the model arrives, and use ideally a laptop tethered to your camera to get your metering exactly how you want it. Take something with some colors (some mixed fruit or flowers if you don't have anthing better) and get a few combinations of exposure settings that work well. Write them down.
If metering is new for you, try setting your camera to aperture or shutter priority and take photos of the same thing from the same place while adjusting aperture values in A mode and shutter speeds in S mode. Notice how the other and possibly ISO (if it's set to auto) change to keep your exposure basically constant.
A flash will add light to your image (which allows lower ISO settings and more flexibility with shutter speed and apature), but flash light can be pretty harsh (which whites out skin tones and emphasises skin flaws), so angling it to bounce off the ceiling (or running an external flash through a softbox or bouncing it off an umbrella will make it softer. Better would be using several light sources (at a minimum natural lighting and an off camera flash).
At times, using low key lighting (lighting only from one side) can be flattering and create far interesting images.
Once you have your expsure set correctly, you can use aperture and shutter speed to change the look of the photo to suit your artistic vision:
Changing aperture (and compensating with other factors) will reduce depth of field (the amount of the picture that's in focus, larger apertures (f/smaller numbers) will leave less of the photo in focus.
Changing shutter speed (and compensating with othr factors) will cause more motion to be captured. That can be good if you want to suggest movement, but is rarely an effect that looks nice in still photos of people. Try to keep your shutter speed faster than your focal length. A tripod will help, but remember that your model won't be perfectly still either.
Changing ISO means your sensor will use less light to make a decision on brightness/color, so there's more room for error. We call this error noise or grain. If you haven't, during your metering shots, try taking a few photos that expose properly at different ISO settings before hand (so you'll have to be adjusting your shutter speed or apature to compensate). This will give you some idea of how much of your ISO range will be useful. Most digital cameras can peform reasonably well up to ISO levels of 400-800 (better ones look good beyond that).
Please ask more questions, but realize that this is normally something that's easiest to learn if you're shooting pictures with different settings to see how they impact your photos.
