How to change the default sort order in a views table?

Hi, I created a table using Views and marked some fields as sortable. But when I click on a sortable field, the default sort order is ascending. Thus, I need to click twice to sort the table in the descending order. But as most of the fields I intend to use as sortable represent some performance indicators, I'd like them to be sorted in the descending order by default (at the first click) so that the "best" nodes appear on top of the table. Moreover, as some tables may be quite long (with long SQL runtimes), having to click twice to get the needed result is going to be very annoying for the users.

How can I achieve that? Ideally, it would be great to be able to choose the default sort order for each field, but if it's a lot of work, I would be ok with changing the default order setting for the whole site.

Thank you