For onwards travel, sample fares include Maumere 50,000, Ende 30,000 (bemo) or 35,000 rupiah (bus), Bajawa 100,000 rupiah and Ruteng 150,000 rupiah.
Ask at your accommodation for assistance -- as you'll need to flag down the correct transport as it passes.
Assuming you don't have your own transport, there are two main ways to reach the summit. You can hire a bemo for 200,000 rupiah (for two passengers, price increases incrementally if you have more than two) for the trip there and back or an ojek will take a single passenger there and back for 100,000 rupiah. Expect the trip to take around 45 minutes to the carpark and then it is another 20-30 minute walk to the viewpoint.
If you're coming from Ende, it's about two and a half to three hours to arrive at Kelimutu, by way of some of the most jaw-dropping tropical scenery in Southeast Asia. It's an extremely steep road with a lot of switchbacks, and you definitely don't want to encourage your driver to hurry it up.