Making a good impression is as simple as ‘The 4 Ps' Be Pleasant, Polite, Positive and Professional.
This sounds simple, but when nervous and focusing on your acting, can easily be forgotten (especially in the haste of commercial castings).
Always be pleasant to the receptionist (sometimes they will be part of the casting team, especially if at an in-house casting studio). We cannot tell you the amount of times Jen would be short staffed and so hop on reception whilst selecting actors to come in to the next day’s casting and actors would be extremely rude, or bitching loudly about their agents or come late and demand to be seen straight away or moan about the waiting time. Guess who wouldn’t be called in to Jen’s castings ever again! You never know who you are talking to and it really does pay to be pleasant. If it’s a long wait you can always ask politely what the waiting time is and explain nicely if you need to get back to work etc.
When entering the casting room, be open, say hello with a smile and connect to everyone there with your eyes! There is no need to shake hands unless they go to shake your hand, eye contact is more than enough to establish a warmth between you. Let the casting team lead the greeting.
If they ask ‘How are you?’ Ask how they are back! This is very rarely done as actors come into the room in a bit of a self-obsessed state. The casting team are people as well and this simple question opens up a dialogue beyond just getting down to business. If they ask how you are - ASK IT BACK, don’t just say fine, thanks and ignore them. Answer in 1 or 2 sentences, rather than one word answers or rambling on, basically normal conversation.
At the end, say thank you and have a nice day - it sounds simple, but again, is not often done. Try and find out the name of the person running the casting as you leave - ‘Are you XXX?’ can work if you aren’t sure if its the CD or an assistant, they will either say yes or ‘No, I’m so-and-so’. Make a note and if you see them again you can greet them with their name. Ta-dah, connection made and you are more likely to be remembered. Don’t be afraid to speak!
Keep any and all discussion with the casting team positive. Even if you have had the worst journey getting there or only got the script late, please do not moan about it as it comes across as ungrateful and creates a negative environment before you have even started. Keep it nice and upbeat and POSITIVE. If you are late, or the casting team have changed your time for you, instead of apologising or giving reasons/excuses (which brings negativity in), say thank you for rearranging or thank you for understanding or thank you for squeezing me in at the later time etc. It says exactly the same thing as 'Sorry I’m late’, but carries positive vibes and acknowledges that they have helped.
Quickly following any initial hellos, how are yous and thank yous - stand on your mark or sit at the chair provided facing the camera / casting team ready to work and feeling receptive. Feel free to ask if you should sit or stand if unclear. Listen carefully and feel free to ask questions to clarify blocking, camera framing and eye-line before you start so you can really imagine the scene in your mind and deliver what is required. Commercials will have an ident first, do this with a nice, relaxed smile.