How does one scale SQL Server 2008 or 2012?
SQL Server doesn't scale out as such. It scales up.

There are 3 areas to do this, subject to edition limitations


CPU cores
RAM
Storage


And of course, use a higher edition eg Enterprise

SQL Server doesn't shard and any such solution (you can research MySQL sharding solutions) adds complexity and overhead to a system. 

Scaling up one server (+ standby nodes/mirror) is usually quite straightforward with RAM, SSDs, more disk volumes to spread IO, separate drives for tempdb and logs etc

Also, if you find SQL Server is CPU bound then it's usually poor design and/or indexes and/or poorly written queries unless you have a massive load.