There are two main ways of getting around Sumatra - by rail and by road. Trains connect most of the major cities and tourist destinations, but it’s often difficult to get a seat on a train, so if you’re planning to travel by rail, get your ticket at least a day in advance. Where trains don’t go, buses usually do, so you have that option as well, even though it’s often much slower, especially as roads- particularly off the beaten track- are at times in a very bad condition. If you’re adventurous and like your independence you could rent a car and do your own exploration.
To visit the offshore islands of Sumatra, you can use ferries (there are regular services from most Sumatran ports), and within cities or holiday destinations, you can usually hire cars, bicycles and motorbikes to make your way around. There are, of course, buses, taxis and the unique `pedi-cabs’- similar to motorized carriages and they make an interesting albeit noisy way of getting around.