Tune the query. Tune the data structure. Tune the indexes. Keep the statistics up to date. That's about all I can based on the query running slow and that's all the information I have. I'd suggest checking out my book on query tuning in the links below. It covers all these topics and more in depth.
"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