In our paperless age, it is hard to know what a person should bring into a job interview.
Resume. I do recommend bringing resumes, although you will probably never need them. Do use good paper stock if you are going to bring resumes; although it is my personal belief that no one actually cares about good quality paper stock, they will notice if it is poor quality. There is always a remote possibility that you show up on a day when the firm’s email server is down, or for some similar reason, your interviewers do not have a copy of your resume. If this ever happens, they will certainly notice if you don’t have a copy to offer them.
Writing Samples and Other Representative Documents. I have found that only certain types of attorneys are usually asked for writing samples - litigation attorneys and patent prosecutors (who should bring a patent application). Corporate attorneys may be asked to put together a deal sheet, and partners may be asked to present a business plan. However, generally speaking, if a firm wants any of these documents from you, they will ask for it ahead of time, or after the interview, but usually not during. Still, if you want to be prepared for the possibility that you charm the partners to the point where they need these documents right away, feel free to bring them.