The route is varied and beautiful. The hike goes from valley to valley, so the scenery changes often and most days are a rewarding hike. On the other hand, this also means that day hikes can be long. A 'normal' day on the route has about 1000 m ascent to the pass and a similar amount descent and a distance of 10-12 km, but on some days the altitude gain or loss is more than 1500m with a hiking distance distance of around 16 km. On such days, it pays off to start early. Also be mindful of the sun: in particular on longer days, the exposure can be tiring and it is a good idea to rest in the shade whenever possible.
Most of the route is not technical; sections near the mountain passes can be a little steep, or exposed, but no special safety equipment is needed. Before setting off on a long route like this, try a few day hikes or a weekend with one or two nights in the mountains to gain experience with the hiking, your equipment/outfit, etc.
Lodging varies from mountain huts and Posto Tappa to hotels that often offer special deals for GTA hikers. In our experience, it is not necessary to book lodging far in advance. However, it does make sense to plan a few days ahead, in particular around weekends and in busier valleys. In most places, the owner/host will be happy to help with reservations, calling ahead to the next town, and may be able to suggest alternatives if a place is fully booked. The cost of half-board accommodation is normally between 40 and 55 euros per person. In some places, you pay separately for the bed (10-20 euro per night) and for meals.
There are many resources with in-depth discussions of hiking gear as well as advice for what to bring. Please look around and check what others have to say about this topic and adapt to your needs. Here is a short list of notes from our experience.
There are various other online and written resources about the GTA. We try to keep a somewhat complete list here, so feel free to suggest additions.
When hiking the GTA, having a guidebook is highly recommended. Recently, some Italian guidebooks have appeared, but there are also some excellent (and often older) guidebooks in other languages.
These are some other websites about the GTA
Other mountain hiking sites