The summit of Mount Lawu (puncak Gunung Lawu) is 3,265 metres (10,710 feet) above sea level. The nearest town is Tawangmangu, Central Java, the nearest major city Solo.
Do not climb Mount Lawu unless you are fit, and do not make the ascent alone. Before departure make sure you are wearing or carrying warm clothing and a waterproof jacket. The temperature on the upper slopes of Mount Lawu can be cold, falling to near freezing at night. Hiking boots or strong shoes are essential, and walking poles can be helpful. At least part of your stay on the mountain will be at night so carry a strong bright flashlight and/or headlamp with plenty of backup battery power. Don’t forget a first-aid kit (including sunscreen), food and plenty of water.
From the Tirtonadi bus terminal in Solo take a bus to the mountain town of Tawangmangu, a distance of about 40 kilometres or 1.5 hours. In the bus terminal [7°40’9.52″S 111° 7’9.72″E] opposite the main market in Tawangmangu look for a mini-bus heading for Sarangan. Ask to be set down at the Cemoro Kandang roadside base station [7°39’48.74″S 111°11’10.78″E] about 10 km or twenty minutes from Tawangmangu terminal. The Cemoro Kandang route is the most easily accessible of several routes to the summit.
At the very basic Cemoro Kandang entry point you register, get a leaflet (in Indonesian) with basic information about the climb, and pay a small entry fee of Rp.10,000 or about $1.00 US (at the time of writing). The track to the summit is narrow and rough. It is very steep in places. It can be muddy and slippery in wet weather. The distance to the summit is about ten kilometres and (depending on your speed, level of fitness, and the time you spend resting) it will take around eight hours. There are several very basic, concrete block shelters along the way where you can rest and sleep.
At the summit there are half a dozen sacred sites: pools, a sacred rock, an invisible market, a place for communing with the saint of the mountain, Sunan Lawu, who is a transformation of King Bråwijåyå V of Måjåpait. These are detailed in the information leaflet. Since my climb in 2001 a number of simple buildings have been erected on, or near, the summit and the sacred sites are better marked than they used to be.
An annual mass pilgrimage to the summit takes place on the eve of the first of Muharram, also called the first of Surå. Check the “standard” calendar date by asking local people or going online to gregorian-hijriyah date converters like http://www.muslimphilosophy.com/ip/hijri.htm. You can also get general information about the climb online, see for example: http://indonesiaexpat.biz/travel/climbing-mount-lawu/ (in English), and http://infopendaki.com/jalur-pendakian-cemoro-kandang-lawu/ (in Indonesian).