You can use "Urgency" and "Deadline" parameters to define the sequence in which requests are processed.
"Urgency" (high, medium, low) determines if a request is to be processed first or not. You can edit the list of urgency values in Hardware Inspector or Hardware Inspector Client/Server. Choose Catalog > Service Desk> Request urgency .
Deadline is the date and time by which a problem is to be solved. Delayed requests are marked with colour.