Under App Setup | Customize | Search | Search Settings
Search Settings

Modify your organization's search interface with the following settings:
Number of Search Results Displayed Per Object:

Lookup Settings:

Select the objects for which you want to enable the following features and click Save:
- Enhanced lookups provide an updated lookup dialog interface that gives users the ability to filter, sort, and page through results as well as customize columns.
- Lookup auto-completion displays suggestions from the Recent Items list as you type.