Traditionally, actors/actresses have used 8x10 Black and White Prints as the standard headshot. But, even though B&W 8x10 prints are still used, it's become more acceptable and more often preferable for actors/actresses to use electronic format Color Photos for their headshots. They stand out from the rest of the gray and white washed photos, and it’s much more convenient to file.
A couple of months ago, a good friend of mine needed some headshots taken on short notice, so I just took them in full color and had them enhanced and burned onto disc for email. At the beginning of the week he sent them off, and he's gotten alot of job offers since then.
Another friend of mine who's an aspiring actress in LA told me that she and a number of her friends have been modifying their portfolios to the electronic/color format as well. It's not as much of a creative decision for them as it was for me; it’s more of a necessity for them, but still effective either way.
The general cost for headshots can range anywhere between $250 and $1000, and that may or may not include prints.
It depends on where you are, what’s offered in terms of quality, creativity, and rates i.e. hourly, daily, etc.
If you have a friend who is a photographer, then I strongly suggest you try to go through them first. Friends generally don’t charge, or at least they shouldn’t, and they’ll work with you to get the perfect shot. When you go through someone you know; you’ll more than likely only have to pay for the print work. My sister, who’s a Houston Rocket’s Power Dancer had to update her portfolio recently, and because she’s good friends with a photographer, she was only charged for the prints, which totaled up to be less than a hundred dollars.