Deciding which phone rings. Everything else — queues, skills, overflow — is a variation on that one sentence.
Most products dress these up with different names, but there are only really four patterns and you will use two of them.
Routing by skill sounds obviously correct and fails quietly, because skills get set once when somebody joins and are never updated.
Six months later the routing is sending invoice questions to somebody who moved to admissions in March. Review the skills list when people change roles, or do not use skills routing at all.
Sending a caller back to the person they spoke to last time is usually worth more than any clever distribution. They do not have to explain themselves twice.
It only works if the call history is on the customer rather than in a call log, which is the thread running through most of this blog.
Tell us what you need — education, study abroad, healthcare, property, technology, marketing, recruitment or outsourcing — and the right team will come back to you.