Syllables are always constructed beginning with a consonant. Then a vowel follows. The syllable could stop here, or there could be another vowel, or consonant, or both. The syllable begins with the initial consonant on the left or top and the vowel(s) and other consonant(s) follow to the right or bottom, like this:
가 where ㄱ "k" is the consonant, and ㅏ "ah" is the vowel. It is pronounced "Kah".
고 where ㄱ "k" is the consonant, and ㅗ "oh" is the vowel. It is pronounced "Koh".
When constructing syllables, always move from left to right and top to bottom. This is the same for reading. Sound out the initial consonant and then the following vowel(s), making it flow into the other ending consonant(s), if any. It's just like reading in English. Read left to right, sounding out each letter. And there you have the pronunciation of the syllable. Then move on to the next syllable. Words are separated by spaces, and syllables are right next to each other. Again, just like in English.
달 where ㄷ "t" is the consonant, and ㅏ "ah" is the vowel, followed by another consonant, ㄹ "l". It is pronounced "Tahl".
돌 where ㄷ "t" is the consonant, and ㅗ "oh" is the vowel, followed by another consonant, ㄹ "l". It is pronounced "Tohl".
When writing Hangul, start in the upper left of the letter and move left to right, top to bottom. Always write the characters in this manner. If you practice this way, then as you write more and more, your Korean writing will become more natural. This way even your quickly and messily written Hangul will be legible to Koreans.
Above is a brief chart showing the construction of every two-character configuration. Do you notice that there are some vowels missing? That's because those other vowels are dipthongs, which are sounds made from two vowels next to each other. We do the same in English, as in "o and "u" put together make an "ow" sound as in "out". Study this chart and check out the dictionaries, and you'll find you can sound out the syllables.