My flight was from Germany to Jakarta both way. Besides that I haven´t planned anything. I usually just take my stuff, go and see what I feel like doing when Im there. My travel route eventually happend to be Jakarta – Yogjakarta – Malang – Denpasar – Ubud – Yogjakarta – Jakarta. I took the train for all these routes except for Ubud – Yogjakarta I took the plane. Flights within Indonesia are really cheap so I recommend checking that out and considering to take flights for longer distances. But I like taking the bus or the train and that way watching the landscapes passing by and getting in touch with local people on the way. I always choose economy class, its much more exciting. I had some beatiful moments in the train where I sat with old indonesian farmers who all had food and once they saw I didn´t have any they all started sharing their food with me and smiled and laughed with me without understanding each other. I love moments like these on my trips. It really touched me that people that have so little share their food with me without even thinking about it and without expecting anything in return.
In Indonesia everything was really easy to organize. For major activities such as hiking up volcanos I booked the trips through the hostels I stayed in. Almost all of the hostels offer it. It is also recommendable to rent a scooter and explore places on your own. You just have to be ok with the extremely chaotic traffic. During my trip I was lucky enough to make indonesian friends and they took me to many places that were unknown to tourists. But most of the places are easy to reach with scooters and with Apps like mapsme it´s easy to get around, explore unknown areas, find hidden beaches and see some authentic indonesian life.