Behavioral questions, and lots of them.
HR may not be present; the company may rely on the discretion of the hiring manager.
You may be a Contractor who can be terminated on any given day; in this case, HR may not be present in the hiring process.
It may be an unstructured interview, somewhat informal, and relatively easier to succeed if that happens.
But why take that chance?
Start now, learn, practice, refine, rinse and repeat.