Your best bet is to name your reports so you know when and where they are used. For example if you have a drilldown report named it "Drilldown - Report Name it Drills Down From".
As far as embedded reports on forms where they are actually from another table I try and label those accordingly as well based on where the report is used. For a record picker it would be something like "Record Picker - Table Name - Form Name" and even add on to that if need be if there are several in use on the form.
Just label the very important ones. I don't bother with most reports, just ones I know I need to keep to make sure the forms and everything function.