Use your Windows client's basic defragmentation utility
This is a fairly obvious tip, I think. Workstations with ever-changing data stored on the local hard drives can and do develop substantially fragmented. Increased fragmentation on the local hard drive can have a negative impact on performance for read/write-intensive applications such as Outlook where Outlook is using either personal folders (.pst) or offline folders (.ost). For fully patched Outlook installations that are responding poorly, don’t forget to verify a good workstation drive defragmentation status in your troubleshooting steps.
To maintain optimal Outlook performance, local drives should be defragmented at the file level regularly—monthly or even weekly for busy workstations. Almost all Windows clients come equipped with a basic defragmentation utility, and recent versions allow for scheduling of defrag operations. Of course there are centrally managed enterprise utilities that provide more comprehensive remote client defragmentation and relevant reporting.