QuickBooks only tracks completed sales transactions. You may want to keep track of sales leads and interactions with those leads and customers. Customer Relationship Management (CRM) software can help you keep up with follow-ups and send bulk marketing emails. Project management software allows you to schedule and track an multiple stage project and collaborate with co-workers. There is industry specific CRM for construction, field-service, and e-commerce, but a basic CRM can be useful for service business like real estate agents - and bookkeepers!
Insightly offers basic, affordable Customer Relationship Management and Project Management. There's a limited free version for two users (click on button above for their website) so you can play around with it for as long as you want.
With Insighlty, you can track leads to opportunities to projects with pipelines, stages, and activities. "Organizations" in Insightly sync with QuickBooks Online customers when you decide they should. Organizations in Insightly can have multiple contacts. You can assign custom fields and tags to sort and filter however you want. You can create "Events" and forward emails and attach them to contacts and organizations. This is very much like the old phone log I used to keep - a customer history in one place. You can even attach documents. You can do bulk emailing and set up templates. The full version integrates with MailChimp for more design-heavy templates.
What Insightly doesn't have that some others do is invoicing, although you can see an organization's payment history pulled from QuickBooks. Unless you have special invoicing needs (see construction) I think this is better done from QuickBooks. Some pricier apps also have login portals so customers can see their order and payment history.
I use Insightly to keep track of various repeating tasks for multiple clients. I can see quarterly sales tax due dates on the calendar, and a list of all clients that need it on my task list. I can also look at a client and see a list of all the services I do for them. And, I can see what I've finished and checked-off.
I recommend trying the free version of this software and seeing what it can do for you! I can help you get set up and running with Insightly!
The apps I'm recommending here I have used or seen in action, and work well with QuickBooks Online. I am committed to continuing exploration of new and promising "software as as service" apps. Not all the apps in the QBO app store live up to their promise, and not all are being maintained and updated. I hope I can help sort through them and find ones that can truly help. While learning something new requires time and effort, keep in mind the time consuming tasks that the app will replace!