How to delete all items from list?

if you have list with more than 500 items, and you don't want to chose coding path, and don't want to delete list as well, than you go to "Manage Content and Structure" view, it allows you to view 1000 items at once and than select all delete all.

You can delete all items at once in a Datasheet view (Ctrl+A > right click on the row > delete row).

In your SharePoint site you can go to your list and You can click on the checkbox beside the first item on the list (It should highlight all of the items) and then click on "Items" in the List Tools ribbon and you will see a delete button.

If you don't see the checkboxes edit the view by clicking on "List" in the Tools Ribbon and then go to modify view. Scroll to the bottom of the settings and you shoud see "Tabular View " and enable checkboxes.

That should help. :)