The Amazon Relational Database Service for SQL Server now supports the Microsoft SQL Server Database Engine Tuning Advisor. The Advisor will help you to select and create an optimal set of indexes, indexed views, and partitions even if you don't have an expert-level understanding of the structure of your database or the internals of SQL Server.
You will need to create a representative workload (a set of Transact-SQL statements) to run against the database or databases that you want to tune. The workload can be stored in a file or in a database table. Either way, the workload must be structured in such a way that the Advisor can execute or replay it multiple times. You can, if you'd like, generate the workload by performing a trace against your DB Instance while it is supporting a real or simulated version of your application.
To learn more about how to use the Tuning Advisor, please visit the Common DBA Tasks for Microsoft SQL Server section of the Amazon RDS documentation.