For our Company, one key activity is supporting our Customers when they have a support issue. For every such issue, we generate a Case in Microsoft CRM and track the same.
Similarly, if there is any inquiry from Customer related to billing or adding or removing a service, we generate an Opportunity in our Microsoft CRM to track the same.
It is quite possible that this may be relevant to many of us. In that case you can use a good CRM system like Microsoft CRM or any equivalent system to remain on top of your issues.