Cresent Mountain can be approached via the north trail or the south trail. I took the north trail. South trail is described here. Crescent Mountain - Hike Oregon
You can get to the trailhead for the south trail by taking Lava Lake mdw road off highway 22. (44.4859,-122.00008)
After 2 miles you will come to a junction you will take a right here. (44.47497,-122.01838). You will see a sign pointing to Cresent Mountain. If you go this way it will lead you to the south trail head. Travel about 3 miles and take a left. (44.49195,-122.05727) You will travel little over a mile to the trailhead. There is a small parking area, room for a half of dozon cars or so. (44.48625,-122.07932) Hike roughly 4 miles to the summit from here. Nice views and plenty of room to operate. There was a lot of people on the summit. All came up the south trail. I had the north side to myself. this trail is open to mountain bikers as well so keep an eye out for them.
This is part of the Old Cascade Trail area. Willamette National Forest - Old Cascade Crest Trail Area (usda.gov)