Check for duplicates upon entering new record.
It would be extremely helpful if while entering a new lead for instance, when you typed in an email, phone number, or last name, the system would scan in the background for records containing the same data.
Maybe at the top of the screen it would drop down an alert that says "Similar leads(s) found. Click to view." and it would give you the option to view the lead(s) in a new window/tab.