Hmm.. If there really aren't any native koreans that you know who can correct your prounciation then I guess the next best thing is to watch/listen to korean podcasts specifically created for individuals learning korean. These will allow you to hear the way words/sentences are supposed to be pronounced and since they're catered for people learning the language the speaker will repeat the sentence or words several times. Korean101 has a good selection of podcasts the last time I checked. It's been a long time since I checked their site but if you can't find any suitable for you Korean101 a quick google search should provide you with many other options.But what I would suggest you do is listen to the way the natives pronounce the words and try and mimic the tones and intonation. Or even better, why don't you try contacting a native korean from this site and see if they would be willing to talk with you on skype? That way they can directly correct you. The problem with the podcasts or audiotapes is that you may THINK you're pronouncing it correctly but you may be stressing the wrong parts of the word. In return, if they're learning English perhaps you could help them with their English. You could just contact a teacher on this site on the other hand. It's entirely up to you.