An agent, publisher or publicist may prefer you bring a proof sheet so they can pick which pictures they feel are best to sell you. Avoid having your photos retouched. Comparison-shop, but avoid the cheapest places. Get 8x10 photos. Newspapers always want that size, no matter what size they print it.
Lithographed photos are acceptable and much, much cheaper than glossies.
Have them print your name on the front of your photo. Print a hundred. Include all three of those things or it will get thrown away. Send ten at a time. Do a file card that says when you sent them and write a note on your calendar to call them in 14 days.