Sentiero (italian for "path") 452 offers a nice hike up to the summit of Nuvolau, enjoying along the way the beauties of the mountain group formed by Nuvolau, Ra Gusèla and Averau. It's not a difficult path, you will be able to reach the Forcella Nuvolau (where the rifugio Averau stands) just by walking along a good path and a wide dirt road. After the Forcella, all you will need to do is turn uphill towards the east/southeast and follow the usual crowds up to the summit. If you feel uneasy when surrounded by so many people, just keep going and enjoy the sights. Croda Da Lago, Cristallo, Tofana di Rozes, Averau and many more will make up for it.
Passo Giau, the trailhead for this route, is a wide col placed on road SP-638 between the italian villages of Pocol (in fact closer to a neighbourhood of Cortina d'Ampezzo) and Selva di Cadore, about halfway between both. That means about 14 km away from any of them. There's a wide parking area at the pass, but it can get full rather soon during the high season, making it advisable to start the hike early. Apart from private vehicles, there's also a public bus (Dolomiti Bus) that goes across the Pass, linking Cortina d'Ampezzo to the small village of Pescul in the Val Fiorentina.
Start walking north from the Passo Giau, following a wide dirt track that leads towards the impressive rocky column of Ra Gusela. When you reach the TV and mobile phone antennas under Ra Gusela, the track disappears and is substituted by path 452, marked (towards your left) by a wooden signpost and paint marks on the rocks. The first section after the antennas is a little bit twisted among rocks, but soon turns into a good path that leads northwest under the cliffs. There's not a big altitude gain along this path, but when you reach its end under the Forcella Nuvolau it will come to a wide dirt road originated by the ski lifts and huts needs. Enter the dirt road to reach easily the Forcella Nuvolau, placed between Averau and Nuvolau and serviced by a big new hut and a ski chair lift (open in summer time). After that, just turn right (grossly east-southeast) and walk uphill in rocky/scree terrain. You will get to the Nuvolau hut (at the summit of Nuvolau in an additional 45 to 60 minutes.
There's an alternative small path (see the .gpx file) you might use to reach the Forcella Nuvolau from sentiero 452. You will be able to see it to your right when the path almost joins the dirt road and you are positioned under the Forcella. Be extremely careful if you decide to follow this tiny path, it's steep, might get tricky if wet and there's a spot where a little bit of scrambling (grade I+ UIAA) could be necessary. If you are not absolutely sure about your ability to cope with this conditions, please follow the main dirt road to the Forcella
There are no special recommendations for summer/autumn climbs, when the mountain is not covered by snow. I assume that mountain boots, rain gear, food and water are always included in your backpack, of course. If you happen to be climbing Nuvolau in winter time, please do not let yourself into self-confidence and carry full winter gear (ice-axe, crampons, gloves and so on...)
"Never lower your flag, it's never the last enterprise"
--Sir Ernest Shackleton