Planning is exactly the same as for any other protocol. Documentation of the business process is the same as with any other protocol. Documentation of transactions (timing samples) is the same as with any other protocol.
What is different with SQL Server is that it speaks so many darn protocols. So your first challenge is to determine which protocol the client is communicting to SQL Server with. Is is DbLib? Is it ODBC? Is it via MSMQ or MTS? Is it via another mechanism. Each different type of communication will dictate a different type of recording/script construction. It might also dictate the types of infrastucture that you monitor during your load test.
When you move to the controller (items to monitor aside) you should have the same challenges as with any other protocl