To change the location of a new custom field, edit the page layout for the appropriate tab.
Using Record Types
If your organization uses record types, edit the record type to modify which picklist values are visible for the record type.
Tracking Custom Field History
You can select which custom fields to track on the History related list of custom objects and most standard objects. All entries include the date, time, nature of the change, and who made the change. History data does not count against your organization’s storage limit.
Using the Translation Workbench
If your organization uses the Translation Workbench, notify your translators that new fields need translations.
Activity Custom Fields
Activity custom fields can apply only to tasks or only to events, or to both tasks and events. For example, you can create one Time Spent field and then add it to both the event page layout and the task page layout.
Mapping Custom Lead Fields
For lead custom fields, you can click Map Lead Fields to specify which custom lead fields to map to custom account, contact, and opportunity fields during a lead conversion.