To delete a list, Control- or right-click on it and choose Delete. You can also use that contextual menu to open a list in its own window, or rename it.

You click on lists to navigate between them. If you use a multitouch input device, you can also use two-fingers wipes left and right to navigate across your lists.

When you're ready to start adding tasks, you again have multiple input options: You can choose File -> New Reminder, click on the next blank line on your list, double-click anywhere below the last task on your list, or click on the Plus (+) icon at the upper right of the Reminders window. As you type in a new task, or after you hover over any task with the mouse for a moment, an i icon appears on the right; click it to configure extra details for your reminder. You can instead double-click a task to accomplish the same thing.

When and where

Among the extras you can set are options for when Reminders should remind you: You can choose to be reminded at a specific date and time, or when you arrive at or leave from a specific location. Reminders in iOS 5 limited location-based reminders to addresses linked to your contacts, though Apple says that's improved in iOS 6. Mountain Lion already allows you to set those reminders to any address of your choosing.