As per our guide, Jeffrey Sifuego of Isarog Guardians, there are 4 known trails from different municipalities; Panicuason Trail (Naga), Patag-patag Trail (Tigaon), Calabanga and Goa.
The jumpoff for Mt. Isarog via Panicuason Trail is at the DENR Station. This is also the jumpoff if you plan to visit Malabsay Falls. During the 10 - 20 minutes hike, we saw few abandoned stations/research offices before leading to the forest. The trail is well established however few diversions can be seen before reaching Camp 1. I guess some of these trails leads to falls and possible streams or somewhere else.
The Camp Sites - There are 4 Campsites with water sources each
Before reaching the highest point, an open portion provides a good view of Naga, this part is called the Vintana.
From Vintana, one has to scramble all the way up to reach the highest point, which is still covered with trees. To get a better view, climb the highest tree and from the top you'll see Mt. Mayon.
For washup, hikers may choose either Girls Scout of the Philippines (GSP) office or the nearby resort.
Other sidetrip destinations would be the Panicuason Falls, Hot Spring or Stroll around Naga City and visit few old Churces.