I've only ever worked in small businesses and never worked in a company that has HR, for example. I'm careful about what I do or say at all times.
The field is really competitive, so I've had to stretch the truth about my accomplishments in a believable way from interview to first week. I've been trying not to get caught up in half-truths, so I just keep my mouth shut about past jobs most of the time.
I'm also making mental notes of all the various social dynamics in the office: Who is trustworthy, who creeps me out, who's a Karen/Kevin, etc.
The job itself is a breeze. I've been able to ace all my assignments. But most of the hard work comes from just preparing myself for social interactions and getting the lay of the land. It's so much easier in small businesses when you know who everyone is and interact with them on a daily basis. In my current job, I have no idea if the owner even knows I exist.