Core
Run a support desk your clients actually like.
Lessons
Raising a ticket, the four priorities, the five statuses it moves through, replying, and closing it properly.
Putting a name on every ticket, what the four priorities are actually for, and why an unassigned queue is the thing that breaks a helpdesk.
The five statuses and what each one means, using categories so the queue tells you where your problems come from, and the difference between resolved and closed.
The queue is internal: your own people raising and resolving. A ticket has no client and no project and nothing billable, so here is how to handle a client-reported problem across the CRM and the queue without inventing a link that is not there.