The entity customization experience in CRM 2011 is similar to Microsoft Dynamics CRM 4.0, which allows you to customize almost all of the entities. However CRM 2011 has made some improvements to the overall customization experience. One of the improvements is that it allows a CRM user who has entity customization privileges to quickly bring up the form customization designer. All you have to do is click on the Customize tab within the entity record, as indicated in the following screenshot:
Additional customization improvements in CRM 2011 are that it allows you to create the attributes and relationships within the designer, it allows you to customize the left navigation items, and it also allows you to drag and drop the fields onto the form: