ezychick and getoutofmygalley:
As far as I know they don't do 'day of a senior' anymore.
Instead they ask you 5 questions like:
Have you ever been in the situation where you had to motivate other people?
or
Tell us about a time when you recieved good/bad customer service. How did that make you feel and how was the situation resolved?
So pretty much they ask questions that are supposed to show your skills in certain areas. An OPM advised me to write down a list of skills that they are looking for in a senior like 'leadership''teamwork''problemsolving' and so on and have an example answer ready for each skill.
Good luck ezychick!