Doing professional head shots, need advice please

I was asked to do a photoshoot for professional headshots of someone going in for auditions. I have no experience in this field and the parent knows this but likes my work and wants me to do them anyways. I have a Nikon D3000 and normally shoot outdoors natural light on Jpeg Fine, Large photo size. Manual. What is the BEST settings to use for this shoot on my camera to get beautiful quality shots up close that can go from wallet size to large blown up size and look amazing? I have never done this. I always do photoshoots of kids, babies, maternity, and up to 8x10 sizes.please, any advice. Thank you

Added (1). To ERICK… I NEVER said I was getting PAID for my photoshoots. I'm BUILDING my portfolio and have not charged anyone for my work… I also have been doing photos as well as been in contests, since I was a teen. So I do have years of experience and great photos. Just no experience in this actual style. Thank you all for the advice as well. I appreciate it.

Google agency websites that represent actors or models. Check out what the competition is doing.

You'll do fine. The Nikon is a good camera and you already know how to use natural lighting. Try to shoot during sweetlight times… A B/W stido type shot with a black background is also a good setting. I would sugest a test shoot with yourself and the timer to get things tweeked out.

There's no such thing as best settings… It will be dependent on the lighting and the look you are trying to achieve…

1- Do keep your ISO as low as possible,
2- Don't shoot TOO wide open (be mindfull of your DoF so f8 or there's about but that depends on light and distance to subject… So on so forth).
3- I guess you don't own any studio lights or umbrellas so go in the shade and use a reflector to fill in (you DO own a reflector right?).
4- Try to keep your shutter fast enough to minimize motion blur (focal lenght vs shutter speed rule of thumb).

Headshots like these are usually shot with large softboxes to get a nice diffused wrap around light… You don't have that.

My final piece of advice is stop doing paid work (I always do photoshoots of kids, babies, maternity, and up to 8x10 sizes) until you actually know what the hell you are doing.