Consulting on Zoho customization and Act! customization falls into several categories. There is an obvious technical aspect of how to customize these CRMs in the first place. But the bigger picture of what and why to customize is where the real meat and potatoes lie. Most CRMs can be used right out of the box, the vanilla experience. Using a CRM right out of the box would be like buying a car and never adjusting the seat position.
Here are some commonly customized sections:
General Data Inputs
Custom modules to hold industry/business specific data
Letter and email templates
Automated workflows and procedures
Reports and dashboards
Any other items specific to the way you do business