Hangeul (한글, the Korean alphabet) consists of symbols representing 14 basic consonants and 10 basic vowels, which can be combined to make all the sounds used in the Korean language.
* Vowels:

* Consonants:

How to write Hangeul characters
When we write Hangeul in a syllabic unit, there are six different ways to combine the vowel and consonant symbols. As illustrated in the following diagram, the individual Hangeul are arranged and proportioned to fit neatly into a square box, and are always read left to right, then top to bottom.

(2) Symbols other than Roman letters are avoided to the greatest extent possible.

Note 1 : The sounds ㄱ, ㄷ, and ㅂ are transcribed respectively as g, d, and b when they appear before a vowel; they are transcribed as k, t, and p when followed by another consonant or form the final sound of a word.
(They are Romanized as pronunciation in [ ].)
Note 2 : ㄹ is transcribed as r when followed by a vowel, and as l when followed by a consonant or when appearing at the end of a word. ㄹㄹ is transcribed as ll.

(e.g.) 구 리 Guri / 설 악 Seorak / 칠 곡 Chilgok / 임 실 Imsil / 울 릉 Ulleung / 대관령[대괄령] Daegwallyeong

3.Special Provisions for Romanization

(1) When Korean sound values change as in the following cases, the results of those changes are Romanized as follows:

① The case of assimilation of adjacent consonants

백마[뱅마]	Baengma	신문로[신문노]	Sinmunno	종로[종노]	Jongno
왕십리[왕심니]	Wangsimni	별내[별래]	Byeollae	신라[실라]	Silla

 ② The case of the epenthetic ㄴ and ㄹ

학여울[항녀울]

Hangnyeoul

알약[알략]

allyak

 ③ Cases of palatalization

해돋이[해도지]

haedoji

같이[가치]

gachi

맞히다[마치다]

machida

 ④ Cases where ㄱ, ㄷ, ㅂ, and ㅈ are adjacent to ㅎ

좋고[조코]	joko	놓다[노타]	nota
잡혀[자펴]	japyeo	낳지[나치]	nachi

However, aspirated sounds are not reflected in case of nouns where ㅎ follows ㄱ, ㄷ, and ㅂ, as in the examples below.

묵호

Mukho

집현전

Jiphyeonjeon

Note: Tense (or glottalized) sounds are not reflected in cases where morphemes are compounded, as in the examples below.

압구정	Apgujeong	낙동강	Nakdonggang	죽 변	Jukbyeon	낙성대	Nakseongdae
합 정	Hapjeong	팔 당	Paldang	샛 별	saetbyeo	울 산	Ulsan

(2) When there is the possibility of confusion in pronunciation, a hyphen '-' may be used.

중앙	Jung-ang	반구대	Ban-gudae
세운	Se-un	해운대	Hae-undae

(3) The first letter is capitalized in proper names.

부산

Busan

세종

Sejong

(4) Personal names are written by family name first, followed by a space and the given name. In principle, syllables in given names are not separated by hyphen, but the use of a hyphen between syllables is permitted. 

민용하

Min Yongha (Min Yong-ha)

송나리

Song Nari (Song Na-ri)

 ① Assimilated sound changes between syllables in given names are not transcribed

 

한복남

Han Boknam (Han Bok-nam)

홍빛나

Hong Bitna (Hong Bit-na)

 ② Romanization of family names will be determined separately.

(5) Administrative units such as 도, 시, 군, 구, 읍, 면, 리, 동, and 가 are transcribed respectively as do, si, gun, gu, eup, myeon, ri, dong, and ga, and are preceded by a hyphen. Assimilated sound changes before and after the hyphen are not reflected in Romanization.

충청북도	Chungcheongbuk-do	제주도	Jeju-do	의정부시	Uijeongbu-si
양주군	Yangju-gun	도봉구	Dobong-gu	신창읍	Sinchang-eup
삼죽면	Samjuk-myeon	인왕리	Inwang-ri	당산동	Dangsan-dong
봉천1동	Bongcheon 1(il)-dong	종로 2가	Jongno 2(i)-ga	퇴계로 3가	Toegyero 3(sam)-ga

 Note: Terms for administrative units such as 시, 군, 읍 may be omitted.

청주시

Cheongju

함평군

Hampyeong

순창읍

Sunchang

 
(6) Names of geographic features, cultural properties, and man-made structures may be written without hyphens.

남산	Namsan	속리산	Songnisan	금강	Geumgang
독도	Dokdo	경복궁	Gyeongbokgung	무량수전	Muryangsujeon
연화교	Yeonhwagyo	극락전	Geungnakjeon	안압지	Anapji
남한산성	Namhansanseong	화랑대	Hwarangdae	불국사	Bulguksa
현충사	Hyeonchungsa	독립문	Dongnimmun	오죽헌	Ojukheon
촉석루	Chokseongnu	종묘	Jongmyo	다보탑	Dabotap

(7) Proper names such as personal names and those of companies may continue to be written as they have been previously.

(8) When it is necessary to convert Romanized Korean back to Hangeul in special cases such as in academic articles, Romanization is done according to Hangeul spelling and not pronunciation. Each Hangeul letter is Romanized as explained in section 2 except that ㄱ, ㄷ, ㅂ, ㄹ are always written as g, d, b, l. When ㅇ has no sound value, it is replaced by a hyphen may also be used when it is necessary to distinguish between syllables.

l. When ㅇ has no sound value, it is replaced by a hyphen may also be used when it is necessary to distinguish between syllables.

 

[Source: Korea.net]