Hopping onto QF9/10 in a month or so and don't want to look like a newbie so what are your tips for handling J like a pro?
When is the right time to put on the PJ's?
Will they try and serve me dinner on departure out of Melbourne?
What's to do in DXB during transit?
Is it the same plane that continues on to LHR?
Who cares if you look like it's your first time? And how could anyone tell, anyway.
Enjoy the lounge, such as it is. The real point of J travel is to earn enough credits to make WP and hence gain entry into the F lounge(s), which is much much nicer.
PJs - once the seatbelt sign is off, go and change. Keep your clothes uncrushed. Do it before they serve a meal, which they will as soon as they can, so that if any sauces or red wine or whatever spill onto your clothing during the feeding frenzy, it's on the PJs, not your good clobber. And likewise change back after the final meal before landing.
DXB. You have roughly an hour before getting back on board the same plane. You'll have to take all your gear with you. There's a transit security and document check, and once through, you can browse the extensive shopping area, or head on up to the lounge. Possibly you can get a shower there, though they usually have a queue of everyone else off your flight, and there aren't that many showers. But I like to give it a decent try, because I usually need a shave at least, and having the full experience sets me up really nicely for the next leg.
The lounge is excellent. And vast. Several dining areas, a quiet room that's about as big as any other lounge I've seen, various computers, reading areas etc. You can board directly from the lounge. They don't call flights inside, but you'll be able to find your gate and hang around there quaffing champers and munching nibblies.
The F lounge is equally vast and amazingly well stocked. A la carte dining, top notch grog, free shoe shines. The decor is a wee bit over the top, and there are some duty-free shops within the actual lounge, and you'll likely get lost, but it's something to aim for. Rack up those status credits!
Enjoy the trip. You'll be comfortable, well looked after, fed and drunk very well, and hopefully clean and rested on arrival.
And, as noted by others, a real wrench to go back to Y!