Mount (Gunung) Semeru is the highest mountain on Java. There is little water on this trekking route so bring enough. There is a spring but its about a half hour walk from the trail and campsite at Kalimati. There is also a lake en route but you will need a way to treat and filter it. If you can manage without a nearby source of water it is advisable to camp at the highest camp on the mountain just before the end of the tree line. The final hike up to the summit is a very strenuous steep hike up volcanic scree. Its like climbing a 12,000 ft sand dune for every one two step toward the summit you slide one step back. The summit is a large flat area with impressive views down towards Mt Bromo. It is not advisable to approach the crater rim for your own safety, and small eruptions occur on average about every 20 minutes.
There is no public transportation to Ranu Pane and you will have to either hire a vehicle or ojek (motorcycle taxi) to get to Ranu Pane and the trailhead from Tumpang or Cemoro Lawang for Bromo. Tumpang can be reached from Malang by Micro bus, Cemoro Lawang can be reached by bus as well from Malang or Surabaya but you likely have to change in Probolingo this route is much longer.