It could be process, your server set-up or your code. Most of the time, it's the code. I've got a book on SQL query tuning that walks you through gathering metrics to identify the poorly performing queries and then walks you through what to do about them.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning