That sums it up very well.
By the way, you're posting a SQL Server 2000 question in the SQL Server 2005 forum. While this question was fairly generic and the answer would have applied to SQL Server 6.5 or SQL Server 2008, if your questions get more specific, you'll want to put them in the correct forum.
"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