By bus/jeepney to Capas
From Manila: To reach Mt. Pinatubo from Manila, take a bus from Pasay or Cubao to Capas, Tarlac (2-3 hours, P190). Get off at McDonalds in Capas.
From Baguio: Take any Manila-bound bus and ask to be dropped at McDonalds, Capas.
From Angeles or Tarlac: Take a jeepney to Capas.
From Cabanatuan: Take a bus to Tarlac and jeepney to Capas.
Once at Capas junction (McDonalds), you can either take one of the many waiting tricycles for the 24km ride direct to the Tourism Office/Starting Point in Barangay Santa Juliana (smaller model of tricycle, seats max 3people) or take a jeepney to Patling (30P) and then a tricycle to the Tourism Office/Starting Point (P60 per tricycle). Be sure to agree the price with your tricycle driver beforehand (P300 return should be possible depending on your bargaining skills), and ensure he drops you at the Tourism Office, and not an unofficial tour operator who will charge you a higher price and pay your driver commission.
The cut-off point for 4x4s to leave Santa Juliana is 10am, if you arrive after this time you will not be able to visit the lake until the following day. (During 16 Jan 2016 ~ 1 Feb 2016, There's military activities such as Aviation Assult Support Execise and Tactical Exercise, Tour can only start between 5am to 7am.)
During the week an average of 40 tourists visit the lake, on weekends this number is far, far higher. If you are travelling independently you may find it difficult to find others to share the cost of your 4x4 (especially on weekdays), as the vast majority of tourists arrive on package tours which usually include water, packed lunch and a visit to a local village.
Please note that searching for Capas in GoogleMaps (March 2014) will result in a location far from the center of town, near Santa Juliana. The McDonalds junction is located at 15.345262,120.593495 - along the McArthur Highway.
On a tour
There are also plenty of tour companies that can arrange everything for you, including transportation from and back to Manila. Some operators like Tripnas or PinayKeyPoint offer shared tours so you can visit Mt. Pinatubo with a low budget since you will share the cost with other travelers.
At the Tourism Office, you can rent out an off-road vehicle with driver that will take you close to the crater (P3500 / vehicle, maximum 5 visitors per vehicle). Additionally, every vehicle is obliged to get a local tour guide (P500 / guide) and you have to pay an entrance fee of P300 / visitor + a Botolan fee of Php700 / visitor. Thus, the cheapest option is to be in groups of five persons, as it would result in a total cost of P1800 / person (including vehicle, fees and guide).
The scenery during the 1.5hour 4x4 ride across the dusty plain, traversing several creeks, is spectacular. Once at the end of the track, it is approximately a 2hr hike to the crater lake. Note that during and after rainy season (July-October), some or all of the track may be impassable and it will be impossible to visit the crater.
If you are travelling independently you may want to bring a packed lunch to eat at the crater. Snacks can be bought from the villagers along the route for inflated prices.
At least 1L of water per person is needed for the hike, 2L advised. Drinks can be purchased for a premium from local village stalls along the hike route.
Santa Juliana, the starting point of the 4x4 ride to the lake, is a small village with few accommodation options. It is best to stay overnight in Capas and catch a tricycle in the morning from your hotel (by prior arrangement) or from outside McDonalds or 7/11.
From the junction in Capas, or anywhere along McArthur Highway, flag down one of the many (24/7) north- or southbound buses, they will be happy to stop for you. There are also jeepneys to Angeles and to Tarlac (P23), from where you can catch a bus east to Cabantuan.