9 hours is not so bad - the cabin crew will regulate you with meals / drinks / lighting etc so it will... um... fly by!
But, wear layers - it can get too hot / cold. I wear a vest top under a long sleeve t-shirt and good quality leggings that wont go baggy. On landing, remove long sleeve t-shirt and you're ready for the heat! But I often pack a spare top in case of crumpling / spills. It's also the only occasion I wear a waterfall cardi - you can wrap it round yourself like an extra blanket. I also take a pashmina - it can be turned into a pillow / blanket / towel (if some idiot spills a drink on you!). Thick socks too. Take shoes off. I wear Ugg Boots and put flip flops in my hand luggage to change into.
Take your make up off after take off - I use wipes - then moisturise, moisturise, moisturise! I put together a (clear, plastic!) bag of mini toothpaste & brush, wipes, deodorant, moisturiser, eye drops, lip balm and strong mints. Some of this you'll have to buy airside due to sizing etc. I also take a hairband in case my fringe is doing my head in. No to bulldog clips - you can't lean back in them!
YY to ear plugs and eye mask too. And a blow up neck pillow (I care not what I look like on a long haul!).
Ipod with relaxation audio books can lull you to sleep too. Books, magazines, big bottle of water and you're good to go!
I've done a lot of long haul and this is practically my checklist!
Happy flight!