focusing on more than one area

I use a rebel xt with a 50 mm 1.4 lens and I've been aiming to always focus on the eyes in terms of shooting portrait pictures but what do I do when I have 2 subjects? How would I get both of their faces to be sharp?

I usually hold down the shutter button halfway to find the right red dot and aim at the face, so I'm not too knowledgeable about other ways to focus with the camera. Also I'm not sure if I'm doing this right, but if I hit my shutter button halfway and focus in on the face, and reposition my shot with the button still held, the focused part will be something else. I thought if I "lock in" that focus it will stay focused? Maybe I'm misunderstand this whole auto focus deal...

Any help would be appreciated, thanks.

Well, the answer is DOF. If both of your subjects are roughly in the same plane, and you have big enough DOF then it shouldn't be an issue. What this means is that you shouldn't be shooting @ f/1.4. You will need a larger DOF, between f/5.6 - f/11 (depending on distance of subject). to ensure that both subjects are in focus. Do not use the wider aperture (f/1.4 - f/2.8) or you will almost assuredly have one of the people out of focus.

I'm on P mode, and when I switch to AV it's set at 4. So if I'm on P mode, is my aperture set for me?

yes, when the camera is set to P, it will find what it's thinks is the best shutter and aperture, which to get the best exposure. Even tho I am no expert when it comes to shooting people, it would be best to set the camera to AV and then you can select an aperture that you will give you the correct DOF.

If you are using OneShot AF, yes, it should stay locked.
Be aware that 'focus-recompose' might not be the best technique with wider apertures...

Thanks for the advice! I'll go mess around with the settings some more