We did this climb (the one that started at 3.30am at the Guides office, you are at the lookout by 6.15am and then you walk the crater for another hour, back down by 10.30am).
As we had a car, we organised it ourselves at the Guide office between Kedisan and Toya Bungkah so we would not get ripped off by the local guys following us on their motorbikes (everywhere you go in the area). We paid 250,000rp each, but later found out that we could have got it cheaper at our hotel, oh well. Our guide actually earned every cent as I nearly fell 3 times and he caught me.
The last hour of the climb is straight up and I got a bit of vertigo and needed to stop to rest a few times (and I thought I was fit). Another guy followed us the whole way carrying bottles of soft drink, it almost made us feel guilty, like we had to buy one, but I don't drink soft drink and he didn't talk at all so, with guilt, we ignored him.
Our guide was friendly and told us his life story how he loved and lost and will never marry as he will never find true love again. His girlfriend ran off with another man 1 week before they were going to marry. I found this a strange story for a Balinese as I believed all Balinese just had to marry and have children but interesting.
I didn't bring a jacket with me and a light rain started at 5am, when we reached the top I was sooo cold, my guide lent me his jacket and just came back to me every 5 mins to get a cigarette from the pocket (he smoked the whole trip up, which was one of the reasons I had to stop a few times as I cannot exercise and breath in cigarette smoke.
The sunrise was disappointing as we had cloud cover so we moved on further up the mountain and sat on hot rocks to dry our clothes, then the fog rolled in and viability was zero so we had to go back down, even though we had paid to go around the top for another hour for breakfast (no money back though, and no breakfast), we had to wait for our guide as he had his breakfast, this was annoying as we wanted to just get moving.
All in all, I would never do this climb again but having reached the top I did feel an exhilaration and sense of achievement, especially surviving the chain smoking guide. I did want to climb more mountains, I think "Everest' blurted out of my mouth at some stage, must have been delirious.
I was surprised to see dogs at the top, very skinny ones, I wished I had more than bananas on me. On the way down we came across 2 very large monkeys they enjoyed my bananas.
The last hour across the lava fields really hurt my legs as you are walking a slight downhill but your muscles have been used to going a steep uphill. It is very slippery on the way down and don't wear good shoes as they get blacked by the lava.
Make sure you take a light jacket and sunblock, we didn't think of this and I got burnt in the morning walking back to the car, the sun was quite intense, which was so strange as it had been so cloudy at the top.
Afterward I slept until our checkout at 12noon, and I really could have slept longer, I don't know how people do this climb and then do other activities.
Suggested what to bring:
light top long sleeve, that you can take off when it gets really hot in the morning
wear a t-shirt
Long lightweight pants
small backpack for water and snacks
Your guide will have torches