Ko Samui, is an island off the SE coast of Thailand, famed for its glorious beaches. During the 80' and early 90's Ko Samui was a favorite budget travelers destination, however massive development has transformed it into a resort targeted at European and Japanese tourists on package holidays. Backpackers are increasingly bypassing Ko Samui, heading to the cheaper 'backpacker' island of Ko Panghan ,and the less developed island of Ko Tao.

Main town: Nathon: The island's main town and transport center. Apart from arriving or leaving, people only come to Nathon to take care of official business, collect/send mail from the main post office,shopping, immigration, etc,.
Beaches: Chaweng, Lamai, are the main beaches and resort areas, BoPhut and Mae Nam are quieter but also have reasonable facilities. Recently as development continues, the beautiful and quiet beaches getting vanishing. Do not expect beautiful beaches anymore.

Access:
From BKK by air: There are many flights everyday. the most convenient way to come to Koh Samui, however due to the cost, many budget travelers take a night bus/train.
From BKK by train + boat: There are a few night trains from BKK to Surat Thani and take a bus to Donsok port to take a ferry to Koh Samui. Many travel agents and BKK train station sell joint tickets but it is easy to pay separately and if you buy separately, the cost is the same.
From BKK by tourist bus: The most common way to travel for budget travelers. Many bus companies organize the trip with their own buses and boats. You can buy the tickets on Khaosan road. The costs the cheapest.
From south of Thailand or Malaysia: Travel by bus or train to Suratthani then buy a joint ticket(bus to Donsok and a ferry) at a travel agent.

Arriving:
Usually your boat arrives at Nathon port. Songthaws are waiting at the port and you have take one to go to a beach town you choose. Foreigners are expected to pay much more than locals, 50-100B.
If you do not want to pay the high amount, walk to the main road and try to get one which is running on with locals. But still you are asked to pay more.