Segmenting is key. This is true for contacts (advisors, clients, employees, geographic area, industrial sector, type of services...) but also projects (clients, internal, marketing, cases, HR) etc. Self-populating groups (smart lists) with drag & drop with self-tagging (the item once moved to the list is updated with the list's attributes). Whether you are a small business owner or a mid management director in a large corp, you should have more than one type of project and one type of contacts...