By plane to Kathmandu. Prices vary considerably depending on airline.
A valid passport and entry Visa are obligatory. The Visa can be bought at Kathmandu airport or at any Nepalese foreign office, costs US$ 30 and is valid for 60 days.
A trekking permit is also needed to enter the "Annapurna Conservation Area Project". This costs 1000 Rupie and is available from one of the numerous trekking agencies in Kathmandu.
Best time of year:
The best time of year coincides with the pre or post-monsoon periods, since the this area tends to be fairly humid. March to May and September to November are the most stable months.
The climate in this area can vary considerably since the trek varies between 900m and 4100m in altitude. All types of weather conditions, from tropical to alpine, are to be expected. The temperatures are typical of those at altitude: torrid heat can give way to icy cold and torrential downpours or snowfall at Annapurna Base Camp.
This trek is demanding as the temperature altitude range are substantial.
Normal trekking gear.
A tent is not indispensable but recommended as it may prove difficult to find a place to stay the night during the high season.
A vast array of medicines ranging from disinfectants to anti-inflammatories, pain-killers and anti-diarrhoea.
For further ideas consult Trekking in Nepal by Bezruchka, which has a useful kit-list.
Bibliography and maps
Maps tend to be imprecise but adequate as the actual trekking routes are very obvious. Recommended is "Annapurna" 1:100 000 by the Arbeitsgemeinschaft für vergleichende Hochgebirgsforschung Nr.9. Other maps are available in loco.
This area has described in great detail in many different books. Of these, "Trekking in Nepal" by Stephen Berzuchka and "Nepal" by Wheller and Everist, Lonely Planet are recommended.
For mountaineering literature, don't miss
"Annapurna - First Conquest of an 8000-Meter Peak" by Maurice Herzog and "Annapurna South Face" by Chris Bonington.