This route starts at the park entrance for the Bosque Protector/Pasochoa Reserve. It is not the standard summit route due to it being much longer than coming from the other side near the hydroelectric plant.
See the main page for directions from Quito. It is a bumpy ride so if you have hired a camioneta in Amaguaña, try to be one of the lucky bastards sitting in the cab rather than the bed.
From the park's entrance station, pay the fee ($7), receive your pamphlet, look at the map and begin the hike. It really is a nice park when you aren't being rained on the entire time.
Summiters want to get on, then follow the orange trail to the summit. The going is straighforward if a bit steep and muddy in spots until you arrive at short cliff on the crater rim after about 4 hours of walking.
Officially the route goes right over this. Notice on the little map there is a climbing symbol. Reportedly there is or was also a poor path that contours around the cliffy right side but it was not visible to the author. I believe it has been destroyed by the elements. Here the author had to turn around due to 4 hours of rain and mud working on the cliff. The cliff is not sheer but it is class 4 or 5 climbing. There is a good path above as visible from the summit which leads up and over the significant lesser summit on it's path along the crater rim.
tograd thankfully completes the picture. About 30 metres before you get to the sheer cliff, turn left into the woodland. Some fairly good paths skirt around the base of the cliff - keep by it so as not to get lost. Eventually the paths will turn slightly to the right and rejoin the main path on the crater rim, thus avoiding the tricky and downright dangerous looking climb up the cliff. We managed this alternative route without any problems.
From there follow the foot path along the crater rim over some highpoints and approach the summit via the north rim variation to the standard route.
Note that it is not really feasible to entirely bypass the whole highpoint on the left by traversing to the opposite ridge. Doing so requires serious bush bashing.
Pretty much standard hiking gear. Bring rain gear.