These letters have no easy way of explanation. All you have to do is memorize them.

ㄱ      G/K

ㄴ        N

ㄷ         D/T

ㄹ         R/L

ㅁ          M

ㅂ          B

ㅅ          S

ㅈ           J

ㅎ           H

The letters that represent more than one English letter may confuse you, but please don't worry about it.

Try saying task and dask. There is very little difference between the two and its hard to distinguish between which word has a T or D, unless you really emphasize the D or T in that word.

For now, don't worry too much about distinguishing between the two.

~EDITED~
9/28/2017