There are many ways to tune a guitar. You can use an electronic tuner for an electric or an acoustic guitar. Electronic tuners have an input jack for the electric guitar and a built in microphone so you can use an acoustic. Most electronic tuners are pretty accurate. You can also use a pitch tuner that is like a whistle it has six different pitches E,A,D,G,B,E all the strings on the guitar. You just blow into it until the pitches match. But if you can't afford or get an electronic tuner or pitch tuner you can tune the old fashioned way by 5th fret tuning. 5th fret tuning is an easy and fast way of tuning your guitar. All you have to do is put your finger on the 5th fret on the low E string which is the top string of the guitar and hit it and the A string open which is the second string, simultaneously until the strings match pitch. Then you put you finger on the A which is the second string , and pick it and the D string which is the third string open until they match pitch. Then put your finger on the 5th fret on the D string and pick it and the G string open until the match pitch. Now you move to the G string but put you finger on the 4th fret and pick it and the B string open, simultaneously until they match. Then on the B string put you finger in the 5th fret and hit the high E string open until they match. That is an easy way of tuning your guitar if you don't have an electronic tuner or pitch tuner. But if you have a piano and know where the E note is then you can hit you low E string and the E on the piano until they match then tune the rest with the 5th fret tuning then you will know that you are tuned in standard E tuning.