Hi,
By status, show all the open ones first, subsorted perhaps by date when it was updated and 3rd by date when it was opened.
The important for usability is to have to show open ones first. We always login and have to click to sort.
Please, also consider, as per other posts in forum, after a reply, keep the ticket in the page as it was in HC6, or else if we want to reply and close, we have to click, go back to ticket list, sort again, find the ticket, then close it (or perhaps Reply and close option :))
Thanks a lot,
Flavio