There are lots of hotels on the island and they are cheap even by the standards of Thailand. Christmas holidays is the only time when you need to book accommodation in advance. At other times, most of the hotels are empty. So you can find a suitable hotel right on the beach and ask for an additional discount. If the hotel's owner would be intractable, remember that there are a lot of other hotels nearby.
How to get there 
There are several ways to get from Bangkok to Samui:
1. Direct flight to Samui Airport (USM)
. This way is most convenient, but also the most expensive.
2. Fly to Surat Thani airport (URT)
low-coster. Then get by taxi (1200 bahts) to Donsak Pier
. Then get to Samui by any ferry (Raja ferry
is the best, but other services are also good). It is the best value for money
way of getting to Koh Samui, but takes a little longer time, as the road from Suratthani airport to Samui takes a few hours.
3. Night bus from Bangkok from Khaosan Road
for 1000-1500 bahts. It also gets to Samui via Donsak Pier. This is the cheapest, but also the most tedious option. There are also buses between Samui and Phuket, and between Samui and Krabi.
4. There is also Lomprayah
high-speed catamaran, but this option is useless because of the high cost. Also these catamarans are very seasick at windy weather.
Samui has surprisingly expensive taxi. Therefore, we recommend to hire a bike or a car. Also you may use something like shuttle buses (songthaew
) that run around Samui ring road.
When to go 
Best in February-March, as these months it's usually no rain. Worst - in October-December. Remaining months - as you luck. It may be great weather, or it may be rain for a week. But anyway sometimes you will get the sun.
Water temperature, C
Wind speed, meter/sec
Useful information 
There are lots of cheap cafes in Samui. But sometimes it can be found some expensive places, and sometimes even entire districts with expensive restaurants. Thus before you choose your favorite cafe, some experiments are highly recommended. The estimated cost of a complete delicious dinner - 150-200 baht per person.