User Profile Service Application - Plan for User Profile on SharePoint 2010

A user profile is a collection of properties that describes a single user, along with the policies and other settings associated with each property. Some of the enterprise social networking feature that user profiles support are: my sites, profile pages, people searching, organizational charts, enterprise search, social tagging and audiences.

New user profiles are created in the following ways:

• If an authenticated user does not have a user profile, a new one is created using properties taken from the appropriate directory service when that user initially accesses his or her My Site.
• One or more new user profiles can be created using profile synchronization.
• A custom solution can be developed to create user profiles. 

A user profile is composed of a set of user properties. Each user property provides an item of information related to a user. User property values can come from directory services, business systems, or user input. You can set policies on each user property in a user profile to help govern how the information in that property can be used

Plan of User profile includes: Identify stakeholders, Identify how the profile information will be used, Identify directory services and business systems, Determine which properties to include, Determine property details, Determine personalization settings policies, Plan for capacity