There can be lot of check points, couple of them...
1) Are you dictionary files stored on network drives - move it to local drives.
2) Check the performance at SQL Servers in particular check the disk latency
3) Are any users exporting from smart list a large report and your have not enabled SmartlistEnhancedExcelExport=TRUE dex.ini setting.
5) Disable CEIP
6) Disable dynamics online monitoring
7) Disable home page
8) Disable outlook intergration
10) Disable local drive mapping
11) Review expensive query at SQL Server
12) Review missing index's at SQL Server
13) Read Microsoft KB 898982 on slow performance
14) Read Patrick Roth article on terminal server and internet connection
15) Understand the performance issue with roaming profiles
16) Check if users have enabled dexsql log generation
17) Check the tempdb size in sqlserver
19) check the transaction log size of company db
20) Read Microsoft whitepaper on performance for GP2010
21) Check disk space on SQL Server
22) Check the auto complete setting for dynamics gp
23) Check virus scanning of ctree temp files, and gp program files
24) Review dead lock at sql server
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Good Luck!
Sanjay