In a nut shell, Chris was right on the ball.
Not much to add so I'll elaborate maybe.
The higher the ISO, the noisier the image will tend to look.
The wider the aperture, the less depth of field you'll have.
The faster the shutter speed, the better you'll be able to freeze motion.
Now - decide what you want and what you're willing to give up and choose your settings.
Because you're shooting digital, you can "cheat" and check the thumbs after you shoot and adjust accordingly.
If you choose a low shutter speed and then want to swap to a higher shutter speed - just up one setting for every other setting you bring down.
Motion is always going to be an issue if you are shooting people - so it's often worth upping the ISO to avoid unintentional blur. If you have nothing in the scene that is moving, or you want blur, you can lower the ISO for less noise.
A flash or even a spot light can help illuminate some subjects or dark shadows.
Good luck - have fun!
/Mitch