It sounds like the "aw" in "paw", and it's usually romanized as "eo". Also, it's never written just like that when it's actually used in writing—so you need to add a silent "circle mark" to the left of it, which makes it "어".

BTW: That silent circle mark, or "ieung" as it's called, acts as a kind of placeholder when it goes before vowel sounds which aren't preceeded by a consonant. (I guess you could say it fills in the "empty" consonant spot.) However, when it comes after a vowel, the sound it makes is the "ng" of "bring". So the sound "ing" would be written as "잉". (Would anyone care to make that more confusing, or do you think I did a good enough job of it?)

You can get more detailed info here: http://en.wikipedia.org/wiki/Hangul

I hope this helps. ;)

I think that 어 sounds like an oh, or uh sound. 

Which vowel are you wanting help with?

You have to open your mouth as a pronunce an "a" but you have to say an "o"  it is too easy! ^^ 

PS:Points for the CL pic^_^