Procedures for 2nd interview can vary from area to area, but typically the process is initial interview, aptitude tests, then in depth interview with technical specialist (usually senior manager or partner). Depending on what you covered during your first session, and your seniority, you will have either the tests or the in depth interview. Providing you know what you can do and what you can offer the firm that distinguishes you from other candidates, you should be ok. Good luck.
