The first issue is the big one: Will your credit appear in the main or end titles? This applies to both film and television, but let's tackle the big screen first. Most audiences leave the theater when the credits roll. If your name is buried in the end titles, that sucks. Naturally, all the leads receive up-front billing, but there's plenty of wiggle room when an actor is playing a supporting character. That credit could go either way, so it's my job to fight the good fight and get my client main-title billing.
On the small screen, there's no negotiation about this. Billing is established by how the role is labeled in the breakdown. Guest stars always receive main-title billing. Co-stars and smaller end up in back, where they get squeezed and are almost impossible to read.
Once I secure main-title billing, the next issue is: Will that credit appear on a single or shared card? If we're talking movies, having your name appear by itself on a 50-foot screen is mighty impressive. Your parents will finally accept your decision to become an actor. In a studio film, this type of billing is reserved for the big guns, but if you're working on an indie, you're probably not getting paid much and a single card is well-deserved.
In television, if the part's large enough and your level of experience demands it, I can easily get you a single card. But not all guest stars are created equal. Some are smaller and just there to reveal exposition. Think about all those doctors and lawyers and scientists who explain boring facts to the hero. Those actors usually end up with a shared card. And that's when position becomes important. An agent has to negotiate how many actors will share that card and where each name will appear. So your deal memo might have language that reads like this: "Actor will receive guest-star billing on a shared card in second position, said card not to have more than three actors." You would be stunned by how many hours I spend arguing about things like this.
Movies are even more complicated because there are other issues to be addressed. For example, take a close look at the opening credits of the next film you watch. Notice how some of the actors receive a single card in the main titles before the name of the film appears? That's called above-the-title billing. In a studio film, only stars can get it, but if you're doing an indie, this billing is your holy grail, especially if the movie has any chance of getting a theatrical release.
You know what else I love? Special billing. That's when you see the word "and" or "with" before an actor's name. Hailee Steinfeld was billed this way for her breakout performance in "True Grit." It's a terrific way of acknowledging that the actor is someone of note, even if he or she doesn't appear on the first few single cards.
Now here's a little homework for you. Watch some movies and TV shows. Study the credits. Figure out the correct language to describe the billing. Doing this will make you a smarter actor, and then you'll be able to talk the talk when you start booking some serious work. See you in the main titles!