Always put ‘The 4 Ps’ into practice.
Questions can be a good way to connect and give you time to process direction, so long as they are relevant (i.e. asking about the characters motivation in a 2 second commercial is silly, but asking about where they want your eye-line is good).
The most important thing is to LISTEN!
Don’t be afraid to ask how much of the stage directions they want to see. General rule is that commercials and theatre will use the space, and Film, TV and selftape castings will keep it still and hint at the stage directions
You can acknowledge if something is funny/awkward/silly in a positive way - these things make a casting fun for everyone. Too many actors forget their sense of humour through nerves, so try to keep relaxed and have a laugh. The people in the room are just people, and people that want to enjoy the process and see you do well.
Saying that, I would avoid cracking jokes if you can help it. You won’t be the first, or even the tenth, to have told that joke that day and it gets very old, very fast for the CDs.