How do you know if you have a "junky" guitar? One of the main ways to tell is if you constantly have strings that are going out of tune. It can be very disheartening to spend your precious time tuning a guitar, only to have to stop playing in order to tune it back up.
Note: In addition to having a quality guitar, you will want to change your strings every so often to help keep things sounding crisp and clean. This is especially important if you are playing often.A quality made guitar does not need to be super expensive. I have seen many guitars in the price range of $200+ that sound terrific. My first purchase was an acoustic roundback Ovation guitar. The backs of these guitars are made from a unique material called LyraChord and look great. I loved the powerful sounds it projected and it also stayed in tune much longer than others I had tested at the time. In my opinion, Ovation guitars continue to get better and better over time (some newer acoustic/electric models have tuners built-in!). In addition to Ovation, there are lots of quality guitar makers out there, so take your time to select a good one.
Bottom Line: If you are serious about playing guitar, my suggestion is to definitely go for *quality* over price.