Pay close attention to the attorney's way of doing things and particularly the individual's idiosyncracies. Learn the caseflow and standard deadlines as quickly as possible. Doing so will help you stay ahead so you can anticipate the attorney's needs and help you put work on the individual's desk without being asked for it. Your goal is to stay ahead of the attorney.
The attorney is probably busy, so minimize interrupting the individual. When you go to the attorney for something, come right to the point and be brief. That may mean taking time to compose your issue(s) on your legal pad and working off it instead of ad-libbing.
Whenever you have questions, and you will, practice resourcefulness. Attorneys hate being bothered with questions. So do everything possible to find answers yourself, even if it means consulting outside sources. Only bother the attorney as a last resort.
Good luck with your new job.