Not packing. The EM literature is quite good for smaller abscesses not requiring packing and the added harm (pain, not benefit) done on packing and re-packing. There may be a benefit in larger abscesses, but those should be handled by our surgical colleagues - in league with admission and antibiotics.
There is no reason NOT to initiate source control when surgical management will be necessary though. Drains are also more useful than packing in my own practice - i.e. a Penrose through a linear abscess to be removed in a couple of days.