Configuring physical storage for a Microsoft SQL Server installation
First and foremost, look at your SAN vendor's documentation for recommendations regarding storage for SQL Server.  This really should be your first step as the vendor hopefully has done a lot of this general analysis for you. 

If the documentation doesn't mention hosting databases, do some more digging before you choose to go with Tiered Storage.  Understand how data migration between tiers works on your SAN and how frequently it occurs.  Beware of anything that will run a scheduled job that tracks how active sectors may be during a time frame (often a 24 hour period, but this if often configurable).  I've found that in this scenario when it comes time to migrate the data, that data is often slow to access during the operation.  You'll want to insure this process runs during a period of low db activity (which means don't run this during the same time you're backing up your database).  If you have a database that's active all day, I'd recommend you NOT use tiered storage at all if this is how tiering works on your SAN.  Another problem with migrating data between tiers when this type of analysis is performed is that often times data access patterns change and are not consistent throughout the day.  This can result in data living on the faster tiers that really shouldn't be there.  For instance, when you run Index Maintenance overnight the SAN may flag that data as hot and migrate it to a higher tier.  If those indexes don't get accessed during the next migration analysis window, you're now wasting I/Os on idle data.  Depending on your database usage patterns, this could happen quite often where your data is getting migrated to the faster tier only to sit there idle.

Again, look at your vendor documentation.  I would hope they clearly outline the recommended approach needed for their hardware.  Also, give SAN Storage Best Practices for SQL Server, from Brent Ozar a read.  That goes into much more depth on some best practices and is well worth the read.