There are MANY things that will affect the performance of a report. Here are the things I can think of off the top of my head:
1. Make sure you're linking your tables based on indexes.
2. Turn on "Use Indexes or Server for Speed" and "Perform Grouping on Server". For an existing report, go to the File Menu and select "Report Options". To have this turned on for all new reports, go to File|Options and select the Database tab.
3. Group on Fields or SQL expressions, not on formulas. If you group on a formula, the sorting/grouping will occur locally after Crystal has downloaded the data instead of on the database server.
4. Use Fields or SQL expressions in the Select Expert instead of formulas (same reason as #3).
5. Avoid subreports.
Note: Items 2, 3, and 4 assume that you're connecting to a Client/Server database such as MS SQL Server or Oracle where the db server can handle data processing. They won't help if you're connecting to a file-based database such as MS Access.
-Dell