The "West Couloirs" is my name for the two prominent chutes that head up the west face of Crystal Crag from the vicinity of Crystal Lake. I call the first of these the "Main Couloir" (since it is more prominent and goes higher up the crag) and the second one the "One Tree Couloir" (since it has one big tree near the top). Click on the thumbnail photo below for a visual overview of the routes.
From Lake George in the Mammoth Lakes, take the Crystal Lake trail. This trail switchbacks steeply out of the Mammoth Lakes basin with nice views
over the lakes and out to the Mammoth Crest. up to a cirque in between the Mammoth Crest and Crystal Crag. In this cirque lies lovely Crystal Lake. Above the lake to the east is Crystal Crag, which can be seen clearly through the trees. Above you is the west face, which Secor says has a class 3 route up some ledges (we didn't see it). Angle upwards, contouring just below the face, crossing an easy talus field. Soon you will see an obvious couloir that leads up to a high saddle on the south ridge. This is the Main Couloir. Hike up through sandy scree to the bottom of this couloir. Alternatively, head south about 1/8 mile along the base of the crag until you see another couloir with one lone tree way up near the top (the "One Tree Couloir").
Either of the West Couloir or the One Tree Couloir leads to the south ridge of the crag. Both go Class 3, but I would say the Main Couloir is a more exposed and more difficult climb. Photos of each can be seen below (Main Couloir at left, One Tree Couloir at right -- both looking down from the south ridge). The climb up these chutes is pretty obvious, so I will spare you the unnecessary detail -- just keep going up.
Once you top out on the ridge, follow the South Ridge route
to the summit. If you have ascended the Main Couloir, the route is fairly straightforward -- just drop down about 20 feet below the South Ridge on the other side (i.e., the east side) and angle upwards to the summit over easy class 3 rock.
However, the route up to the summit from the top of the One Tree Couloir is a bit more challenging, as it requires some tricky routefinding in order to avoid 4th and 5th class rock between the One Tree saddle and the Main Couloir saddle. As a result, I would rate these routes about equal in terms of difficulty -- the Main Couloir itself is more difficult to ascend, but the route is easier once atop the ridge. On the other hand, the One Tree Couloir is easier to ascend, but the ridge route is more difficult. Choose your poison.