How do I filter tickets by SLA?

Open the filter panel on the ticket list and use the SLA filter. It offers the buckets Breached, Due within 1 hour, Due within 24 hours, Due later, Met, and Paused, so you can pull up exactly the tickets that need attention next. The SLA column is also sortable, and breach states are computed live. There is no delay between a deadline passing and the ticket showing as breached.