Presumably you want to freeze motion, keep your entire subject in focus and minimise noise - in that order. If you want less noise, you'd have to accept some blur (which as dpollitt said, can turn out nicely) - the blur could be due to motion (slower shutter speed) or focus (narrow depth of field/large aperture).
To start, I'd set a shutter speed that will freeze the action, so I'd probably go for about 1/250 as a minimum. From there, I'd set an aperture that will keep my entire subject in focus - if you're not sure what aperture to choose, try using dofmaster.com, or simply experiment on the day. Finally, I'd raise the ISO to whatever was needed to ensure the subject is appropriately exposed.
If the lighting stays more or less the same and the general composition of your photos don't change, you should be able to stick to the same settings most of the time. However, beware that if you're not in full manual mode, changing compositions and having different background colours can force your camera to over- or under-expose your subject.
Two basic rules about depth of field: 1) The closer you are to your subject, the narrower the depth of field, and vice versa, for any given aperture; and 2) the larger the aperture (smaller f-number) the narrower the depth of field, and vice versa (larger f-number), for any fixed distance to your subject. If you decrease the aperture to get more into focus, you may need to increase the ISO to unacceptable levels (heaps of noise), but that depends on your taste.
Having said all that, please experiment with different settings! It's the best way to discover what does what and could provide you with some creative insight for future shoots.
EDIT: In response to Robin's comment, that's correct. To capture a subject about 1.8 meters tall with an 85mm lens on a crop frame sensor, you'd need to stand about 10 meters away, giving you about a meter depth of field at f/1.8
But keep in mind the camera focuses at the surface of your subject, which has depth itself. A person isn't paper thin. f/1.8 at 10m away from your subject, on your lens, would give you only half a meter of acceptable focus into the subject. With extended arms and legs, you'll want to have an even deeper depth of field. An aperture of 2.8 should do the trick, and if you get closer to capture only half-body or head portraits (which often sport photographers do) you'll probably want to decrease the aperture a little further.
This is all very theoretical and probably not necessary - I'd say fiddle around with the settings until you're getting your desired results.