At one point, Hainan was considered a backwater and used as a place of exile for failed officials.
Today, it is undergoing heavy tourist-oriented development with various international hotel chains establishing resorts, especially in the Sanya area. These days, many wealthy Chinese from the northern provinces own second homes in Hainan, where they move to in the winter to escape the bitter cold that characterises much of northern China. It has been popular with Russian tourists for decades. Now it is being promoted as "China's Hawaii". The entire island has been declared a Special Economic Zone.
Haikou and Sanya have airports with regular flights to various Chinese cities. There are also some flights from Southeast Asia. There is high-speed train serves Haikou's Meilan Airport. See Get around section below.
Trains run daily from Guangzhou, Beijing and Shanghai. The trains are loaded onto ferries to cross the sea with passengers remain in the train cars. The trains stop at both Haikou and Sanya, as well as Dongfang, a smaller station between Haikou and Sanya.
You can also reach Hainan by boat. Buses take the ferry.
Haikou at the North end and Sanya at the South end are connected by three highways — East coast, West coast and through the hilly center. More-or-less any significant place on the island is on, or at least close to, one of these highways. As anywhere in China, there are buses to almost anywhere.
Two railways connect Haikou and Sanya. One is the old western ring railway, and the other one is the new high-speed eastern ring railway. Another high-speed western ring railway is under construction. High-speed trains run between Haikou and Sanya at up to 250 km/h, takes one hour and a half between the two cities.
As the smallest province in China with relatively flat landscape, Hainan is an ideal destination for long journey cycling trip. On the East Coast it has a 300km long national road (G223) connecting Haikou, Wenchang, Qionghai, Lingshui and Sanya. The route, which is packed with most famous beach resorts and tourist attractions, is the easiest ride and most popular among amateur cyclists. The Middle route crossing Wushishan (Five-Finger Hill) takes some more toil to go. While it is possible to ride along the West coast, this area is the least developed and more preparation may be needed.
The local Han Chinese speak Hainanese. It is a variant of Minnan, but differs significantly from other variants and is not mutually intelligible with them. Hainanese is considered difficult to learn even by speakers of other Minnan dialects as it employs many unusual consonants which have no equivalent in any other Chinese "dialects" or Western languages, and has an odd tone structure. Nevertheless, learn a little of the language if you can, as locals are very proud of their language, and even knowing a few basic greetings will get you acquainted with the locals much more easily. They realise that Hainanese is difficult even for native speakers of other Chinese "dialects", and much more so for foreigners, so they'll politely correct any pronunciation errors you make. Hainanese also has dialectal variations between different parts of the island, though the Wenchang dialect is considered to be the prestige dialect, and is generally used in news reports and understood throughout the island.
The Li people, who are the largest non-Han minority on the island, speak a language that is distantly related to Thai and Lao. There is also a Miao community on Hainan, which continues to speak the Miao language.
As anywhere in China, Mandarin is the lingua franca; nearly everyone can speak it with the exception of some of the elderly. Due to the proximity with Guangdong, many locals have a functional command of Cantonese as well.
As elsewhere in China, English is not widespread but some people speak it quite well. Staff at the main hotels and beach resorts will usually have a functional command of English. Hainan is a traditional destination for Russians escaping their winters, so many shop keepers and restaurant staff know some Russian, and much signage is in (bad!) Russian. However, trying to engage anyone in a conversation more often than not will prove fruitless.
The Singapore-based firm Asia Pacific Breweries  have a brewery on Hainan and their Anchor beer is common all over the island. As anywhere is China, a range of both Chinese and imported beers are widely available as well. Hainan also has a number of locally-brewed pineapple-based beers, odd but worth a try.
See the drink section of the China article for information on other booze; Hainan is much like any other province for this.
The island is covered with coconut trees. So drinking fresh coconut milk is a must!
Be very careful with water sports on Hainan. Government regulation of activities such as parasailing, diving, and boating on Hainan is lax, so staff often provide little or no training to customers, and the equipment can be shoddy. Without adequate safety precautions, these activities can be dangerous, and even fatal.
There are regular boats from Haikou to Hai'an and Beihai on the Chinese mainland.
There are also flights to Kuala Lumpur and Singapore.