I do a lot of Salesforce consulting, so I have a specific suggestion: create a report based on Last Activity Date and any other relevant factors for each of your contacts. Since every record has a last activity date, this will keep anyone from falling through the cracks.

I find SF's "tasks" to be very bloated, so for callback related tasks you might just make a custom field "next callback date" and update that, then check upcoming calls via a report.

Good luck!