Probably the single most important tool that an actor has is a good headshot.
It's what you and your agent use to introduce you to casting directors, directors, and producers; in other words to the people who have the ability to hire or recommend you for a job. If you don't have an agent, it is essential in helping you to obtain one. I wasted hundreds of dollars on the wrong kinds of pictures before I finally found out what worked for me. Hopefully I can save you time and bucks with these tips:
First of all, keep in mind that we are talking about "Show Business" here, and that's exactly what it is. We all like to think of ourselves as artists, and indeed we are, but a professional actor is in effect a small business.
One of the reasons that many actors don't succeed is that they don't understand that they are marketing a product, just like any other business. Record stores will sell me a heavy metal CD if I want to buy one, but they aren't going to waste any money advertising that kind of music to an old fart like me. I've learned not to waste my time and money trying to market myself to casting directors as a dark and evil character. Sure, I could play one, but that's just not how most folks perceive me. Therefore I try to use headshots that present me as the "type" they do seem to buy me as.... the cop, the farmer, the friendly guy next door, and I also get cast as the police lieutenant or captain, a lawyer, etc. In movies and TV they tend to use people who are readily believable as the age and type of character the script calls for, and there are plenty of actors out there who will fill the bill.
How do you determine your type? Do a market survey before you put your product, which is your headshot, on the market. Perhaps the best way I've come across is that suggested by Andrew Riley in his fine book "An Actor's Business". I did something similar early in my career, but he has it down to a science, and I'll be quoting him freely. Don't just ask your acting coach (which hopefully is me!) or other actors or directors what your type is, ask the public. After all, who is watching TV or buying movie tickets to see you?
Buy a pack of about a hundred 3x5 index cards and divide them into categories as follows. Take half of the cards and put 16 24 in the upper left hand corner. (Half of all movie ticket purchases and prime time movie viewing is done by people in this age category.) Then write "male" on 25 of them and "female" on the other 25. Put a rubber band around each stack. Divide the rest of the cards into five stacks of ten cards each and label them "under 16", "late 20's", "30's", "40's", and "50 plus" , then divide each stack by gender.
Now go to a place that has lots of foot traffic and start your survey. Dress as neutrally as possible so that your clothes don't suggest an occupation. Wear something that either a blue collar or white collar type might wear to a mall. As you see a person approaching you, try to guess their age, and take an appropriate card from your stacks. Put on your most charming smile and go up to the person and say something like "Excuse me. I'm doing an assignment for my acting class to determine my type. Would you please guess my age? Just whatever your first impression is please." Most people will go along with answering one question, if not, just smile and say "Thanks, anyway." It's good practice for dealing with the rejection that all actors face. When They've guessed your age, then ask the really important question: "Just looking at my face, what does it look like I might do for a living besides acting?" If they say something generic like "student", try to narrow it down to what it looks like you might be majoring in, etc. Then if you are Caucasian, and time permits, you might ask them to guess your ethnic origin. It will help you to determined whether you are perceived as a "Mediterranean" type or "Western European" type.
When your survey is complete, compile the results. Average all the ages guessed to determine the median age you look to people. Divide the cards into stacks for those who guessed above the median and those who guessed below. Put aside those that were exactly on the median age for now. Average the low stack and the high stack and you'll have your age range! Next divide the cards into blue collar and white collar stacks. One stack will probably be bigger. List the times each occupation within the bigger stack is mentioned, and you'll probably find one occupation mentioned more that any other, plus a number of votes for similar jobs. This will suggest the kind of characters you're most likely to be cast as, and that's your first headshot should look.
When you go for your picture, dress as if you were going for an interview for that job. You may have a different perception of what you want to look like but the easiest way for you to penetrate the market is to go with your strongest suit. I've tried desperately to look six feet tall and muscular, but it just isn't going to happen. Go with your strengths! There are several good photographers in the area, some of whom give a discount to ACTors. My students should all have a resource list, and others of you can get one by emailing me. The primary thing is to take charge of the headshot session and make sure the photographer understands that the session is about your career, not the photographers. Call ahead and let them know that you have something specific in mind, the specific type that was determined by your survey. The most important thing is that the picture must look exactly like you. You want the casting director to instantly recognize you from the headshot. Also determine how many shots will be taken ... usually 36 or 72.. How many prints you will be getting, who keeps the negatives, and whether a make up artist will be provided. Most photographers are shooting digital headshots these days (I prefer them for several reasons.) Only light make up should be used... let 'em see those charming wrinkles and laugh lines around you eyes! You should get a contact sheet or photo CD a few days after the shoot, and use it to get several opinions about which two shots best sell your type. I seldom pick my own pictures; I always let my agents have final say, since they will be using them most. Then have the photographer or lab print those two as 8x10's, and again get several other opinions about which one to have duplicated. Nowadays most duplication houses can also print from a CDROM if you've had your shots done digitally. There are several good duplication houses on your resources list. The one many of my staudents use for lithographs use (Pinacle Solutions) has a great package; 150X10s, 150 postcards, and 300 business cards for $212.) Final Print, with three locations in the L.A. area, is my choice for southern California. By the way, eight by ten is the industry standard. I have NEVER been asked for my eight and a half by eleven! Also, thanks to digital photography, color photos have come down to a reasonable price, and that's the choice in Hollywood. Always have your name printed on the front of your picture, in case it gets separated from your resume. Don't print your resume on the back of your picture, either, or if you do, attach another to the back. What do you do when it changes, and you end up with a bunch of pictures with and out-dated resume on the back?