What’s the best way to go about a probation violation

The best way to go about one is not to get one.  If you do get one you should talk to a local attorney.  Missing one meeting isn't usually going to trigger a technical violation, usually its a pattern of behavior.  That being said missing a single meeting is a technical violation.  The APO would not threaten you with jail if this was just a single missed meeting, so I would say its imperative that you are working with an attorney and trying to get back in the good graces of your APO.  APO's are vested with a great deal of power to detain probationers and they often wield it like an axe.