Hmmm...Well if you are using that tuner make sure it is saying the right note and stuff. Second with an acoustic I'm guessing you have to use the little mic on the tuner in which case you wanna be somewhere that is as quiet as poissible. Third if your guitar isn't that expensive I have found that when you tune one string sometimes it throws the other strings out of whack. So as you tune go back and make sure the other strings are still tuned right. other than that I dunno. Good luck and I hope it works out for you. :)