Leave Arequipa towards Aguada Blanca. You will need permits to go through the gates. The road is terrible and it takes you between Chachani and Misti. At a fork in the road where a large sign says National Reservoir Aguada Blanca, take the right fork. You will eventually see the lake and dam. Go to the gate and have someone open it. They will appreciate it if you bring some bread or something for them. Cross the damn and follow the main path. 4WD truck is mandatory. There seem to be a lot of paths that cross. Look at the pics I have and estimate about where you want to be. Base camp is on top of one of the "moraine walls". (There are no glaciers here). Base camp is well guarded from the wind.
Start early in the AM. May want to scout the start of the route. There really isn't a wrong way, but the going is easier if you follow the well worn paths as the whole trail is sand and scree. This will generally be a traverse to the right, under some rock walls where there is a good place to take a break. Continue an ascending traverse to the summit. In the pics I have the pink lines show the ascent. The descent is shown in blue. Basically retrace your steps and either go back to base camp or if you have everything with you, just B-line it straight back to the truck down the fall line. Descent this way is very fast. The whole climb from base camp at around 15k to summit at 19k down to car took me about 4 hrs at a steady rate with time to enjoy the summit and take pics along the way. It can take as long as 6 hrs depending on your condition. Someone told me it took an older couple 9 hours.
Hiking boots. Crampons and ice axe if there is snow. Bring all your water. No rope or technical gear is needed.
Normally this route is used to acclimatize for Chachani, Ampato, Coropuna or nearby peaks, but it can be a challenging day for those just wanting to tag it while in Arequipa on vacation.