There are some things that you should just not be without. One of these is an electronic tuner for making sure that you are always in tune. There are a wide variety of them on the market ranging from very simple to more complex models which can help you tune every string all at the same time. If you intend to play both acoustic and electric guitar make sure that your tuner has both a 'line in' socket (for electric) and a microphone (for acoustic). One like the following should be more than adequate for most players.
If you're just planning on playing acoustic, the following 'clip-on' tuner is worth having.
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