Queues are simple things. There's one simple rule to queuing and that is to stand in line and wait your turn. Many people can't get it right and think 'knowing' someone already queued is a free pass or 'I'm with whatshisface' means instant advancement. I never queue jump, placehold or benefit from queue jumping, so my options are to do nothing but gnash my teeth about queue jumpers or to say something, so I do, and I will tell the person where the queue ends and to join it. They invariably say they know some random in the queue like it matters. I then broadcast in tall man voice that the person is attempting to jump the queue. Queues are not democratic or populist structures. First in, first out.
I am sincerely interested in views about queueing, and in particular, etiquette or rules that do not disadvantage people queuing by themself. In my view things get very complicated when two people enter a store, one immediately queues while the other shops. Shopping further than arms length from the queue is rude. Forgetting items is your own fault. Go around again.