If you want to make the most of it then arrive early, maybe three hours or so. Enjoy a glass of bubbly at the bar in Concorde Room and maybe dine in the Concorde Dining area before your flight. Take a look in the BoardRoom (between the door you come through from security and the champagne bar) and enjoy the Connolly leather ex-Concorde seats As soon as you get to the lounge head to the Elemis Spa to book yourself in for a treatment. A list of treatments are available here. If you wish go and mosy around the other lounges.

Let a member of the crew know it is your First time in F, I never did it (or have done it in hope of getting better service!) but by all accounts it garners a few more smiles and something a little special.

Meal service in F, especially on these longer dayflights is 'on demand' but the crew may not make you aware of this. If you don't fancy any of the second meal options then you can ask for something off the first meal options too. Do this ASAP because the crew eat the leftovers for themselves!

Take pictures if you wish but be turn off the flash, the overhead and gooseneck light you should be able to get meal pics even with the shades down. If you want to get some pictures of the cabin I suggest hanging around after one of your flights, LAX-LHR is probably the better option as LAX immigration tends to be pretty nasty and the headstart from F is very useful.

I might come back to edit the post.