Waingapu is the largest town on Sumba and the capital town of the East Sumba Regency .
Waingapu is the gateway town to Sumba and many visitors arrive here.
Waingapu's Mau Hau airport (IATA: WGP - ICAO: WRRW) is a small single runway regional airport served by three regional arilines.
Merpati Nusantara Airlines  flies here from Bandung, Bima, Denpasar, Jakarta, Kupang, Mataram, Maumere, Surabaya and Tambulaka, with many of the flights stopping at multiple combinations of those cities.
The Pelni  passenger ship Awu calls in at Waingapu twice on its 14 day round trip of Nusa Tenggara. This allows access from Kupang and several other cities in the region. The Awu is by far the safest and best way to reach Sumba by sea.
The ferry experience is very enjoyable. When boarding expect a tussle as the usually friendly and courteous Indonesians will push and shove their way past anyone to get on. If travelling economy class do not expect to get a bunk in one of the many dorm style rooms. The spaces go quickly, so it might be worth taking along a mat to sleep on and a heavier weight sarong for if the weather changes. Quite frankly, it's better on the deck as the rooms are very hot and do have a very strong odour. On the subject of odours, be prepared for the bathrooms. Not well maintained or cleaned very often, just be aware. Wet wipes for washing hands are recommended.
Food is served 3 times a day, just listen out for the words "economy" on the loud hailer. Just follow the crowds. You'll need to take your ticket with you. It's not much, so you might want to bring along your own food; dry biscuits and so on. Bearing in mind the state of the toilets a lightweight diet may be in your favour. Hot water is available for a few thousand Rupiah from the little kiosk.
From Lembar to Waingapu is about 26 hours.
Buses to Waikabubak take 3.5 hours.