By private transfer
You can book a private airport transfer from Milan or Turin in advance. This service is especially convenient for large groups.
Aosta is a small town and, for the tourist, everything can be easily visited on foot.
It can be very difficult finding a good restaurant that is open between approximately 2pm and 7pm in Aosta. Those that are open tend to be very casual, fast-food type places.
All restaurants offer a fixed price menu (menu turistico/menu a prezzo fisso) which is not very exciting but is good if you're watching the euros. Don't forget to keep your receipt. The police can stop you and ask to see it.
For vegetarians and vegans, eating in Aosta, and Italy in general, should not be a problem. Italians are quite relaxed and accommodating when it comes to their cuisine (unlike their French neighbours). At the Aosta tourist office, staff should be able to recommend local dishes that are vegetarian or vegan, or easily rendered so. Pizza is a safe bet as the pizza dough is not made with egg or dairy products in Italy or authentic Italian restaurants elsewhere.
Carbonnade: ground beef meat roasted in red wine.
Lots of local specialities - look for the word Valdostana in the names of dishes. Fontina cheese is made locally.
Notable wines; among them is a white wine, Blanc de Morgex et La Salle. Genepy is a strong liquor.
B&B Nabuisson in the centre of the city (http://www.bedbreakfastaosta.it/index.html) is a good place to stay if you want to be close to everything from Roman remains to bars and restaurants. Friendly staff, and they speak English (and French).
Gran Paradiso is a large national park south of Aosta. Great for hiking in summer and winter sports.