wild orangutan eating banana
Sumatra is the largest island in Indonesia and is located in the western part of the country's territory. Lush green forests, impressive volcanos and beautiful lakes can all be found there. The biggest and most developed city is Medan, where Kuala Namu International Airport is situated. It replaced Polonia Airport in 2013. Sumatran roads are not well developed, as is usually the case in third world countries, therby affecting the comfort of travel. The most common modes of public transportation are bicycle rickshaws called becaks, city opelets (vans with benches for the passengers to sit on) and longer distance minivans. Smoking cigarettes in these is a common practice in Indonesia. Taxis are also available, although they are usually overpriced and rarely use meters. You can find more detailed information about travel in Sumatra below.
Medan to Bukit Lawang.
Travel by opelet number 64 from the city centre. It costs 3000 Rupees and takes around 45 minutes to get you to Pinang Baris bus terminal. Don't go inside, the minibuses stop in front of the terminal. Don't believe anyone trying to convince you to get off at the bakery unless you are prepared to pay double or triple the price. I was told by the locals that "the big public bus will stop near the bakery", but that was not the case. Once outside, I was quoted 50000 Rupees for a minivan, so I had to walk to Pinang Baris. The same thing happened near the terminal, but I finally managed to find a fair priced minivan and made the journey for 20000 Rupees.Transport in Sumatra
Upon the arrival in Bukit Lawang, you will find yourself being dropped off at the small bus station and expected to pay 5000 Rupees to be taken to the riverside. If you are averagely fit and your bag is not too heavy, you can just walk to the destination. To do so, leave the station ,turn left and follow the road straight. It is easy to navigate. When in doubt, ask for directions.
Bukit Lawang to Berastagi.
Hop on the minivan to Medan's Pinang Baris terminal. It only costs 15000 Rupees! Avoid men near the private stand, they ask for at least 25000 Rupees per person. You can just wait on the side of the road in front of the terminal. As the minivans stop nearby, ask around and you will easily find out who's going to Berastagi. Be aware that if someone stands next to you, he is probably after some easy money and the price will be inflated to cover his commission. The right price is 10000 IDR and it gets you to Berastagi in just a couple of hours.
Inside the local bus
Berastagi to Tuk Tuk, Lake Toba without backtracking Medan.
From the main road, Jalan Veteran, near the big cabbage statue, take an opelet to Khabanjahe, it takes 20 minutes and costs 3000 Rupees. From Khabanjahe bus terminal, take a minibus to Pematang Siantar and prepare yourself for a bumpy 2,5-hour ride that costs 20000 Rupees. From Siantar take minivan to Parapat, it takes 1 hour to get there and will set you back 10000 Rupees. Get off in Parapat's Tiga Raja Market, this is where ferries to Tuk Tuk depart. Ferries operate every 30 minutes, from 8:30 in the morning till 18:00 in the evening and cost 10000 Rupees.I'd advise stocking up in Parapat Market or in Siantar. Samosir Island is rural in character and offers mostly small, tourist oriented restaurants and bookshops. 
Batak women in Lake Toba
Medan to Siantar by train.
It's possible to get to Lake Toba by Siantar Express train. It leaves Medan station daily at 14:30 and arrives in Siantar around 19:00. It costs 40000 Rupees. There are also trains to other destinations within the island and they cost between 9000 and 70000 Rupees. 
Medan to Banda Aceh.
Non-stop night buses are available and take between 9 and 13 hours. Tickets can be purchased in advance from any of the private bus companies that have offices in the city center, near Jalan Gajah Mada. Expect to pay anything between 100000 and 20000 Rupees. Alternatively, there are regular flights between the two cities and they are not necessarily much more expensive. The flight takes approximately 1 hour.