If one of the strings on your guitar is relatively tuned, you can tune the rest of the strings relative to it. Here's how you do it:

Preliminaries: You will need the help from a tuning fork to get your first note in tune. The most common kind of tuning fork for guitar is one that is tuned to "440 A". That is, the fork, when tapped at the fork end, will vibrate 440 times a second producing a high A note. You can use this note to get the A or 5th string of the guitar in tune.

One way to produce this 440-A exactly on your guitar is by playing a harmonic at the 5th fret of the A string. A harmonic is played by lightly touching the string exactly over the fret with your 3rd finger. Use the part of your finger directly opposite your finger nail, that is, don't play with the tip of your finger, but slightly down from the tip. Once the harmonic note has been sounded you can lift your finger away from the string - it is no longer needed to make the harmonic sound. This will take some practice for some, but it is certainly worth the effort. Harmonics give forth wonderful bell-like sounds and can be very musical indeed.

1. Once you have your A string in tune, press it down at the 5th fret. This fretted note is a D and as you can see from the diagram above, it should be the same pitch as your open D string, the 4th string. (The arrows on the diagram above are used to indicate this equivalence relationship between fretted notes and open strings.) Use this fretted note as a guide to get your D string in tune.

2. Once your D string is in tune, stop (which means the same as press or fret) the D string at the 5th fret. This fretted note is a G and just like before, it is used to generate the same pitch for the next open higher string on the guitar - in this case, the 3rd string.
    
   Compare the pitch of the fretted G with the open G by playing both notes simultaneously. You'll probably need to turn the tuning peg for the G string to bring both notes to the same pitch. You're in tune when both notes sound exactly the same. Please note: the G string happens to be the sexiest string on the guitar for obvious reasons.

3. Now comes the hitch - there's always at least one. Stop the 4th fret of the G string, not the 5th fret. This note is a B and its pitch should be the same as the next open higher string on the guitar, the 2nd string. Use this pitch and the method described in the previous steps to get your B string in tune.

4. Now stop the B string at the 5th fret to get the pitch for your high E string. (Yes, we're back at the 5th fret again.) Use the same method described above to tune your high E string relative to the fretted B string.

5. At this point the only string that is theoretically not tuned is your low E string. Simply use your high E string as the reference note to get your low E string in tune. (One way to do this is to play the harmonic at the 5th fret of the low E string. This harmonic should be the same pitch as the open E string.)
    
   When you have finished getting your low E in tune, check the make sure that the fretted note at the 5th fret of the low E string is the same pitch as your open A string. If it is, you have tuned correctly or are at least are pretty close to being in tune.

6. Play a couple of chords to see (hear) if you are in tune and make any fine tuning adjustments where they are needed. You are now in standard tuning - (E A D G B E) and ready to rock-n-roll.

This might sound crazy, but people need to practice tuning. Tuning your axe is an essential skill needed by all great musicians. After all, if you can't get it in tune, you won't sound good. I've seen some great guitar players tune their instruments in the middle of a guitar solo in a split second's time without missing a beat. Very cool indeed - a sign of a true master. These guys really know how to listen to their instruments while listening to other musicians they might happen to be playing with as well as listening to the overall sound of the music that is being created. A musician needs to be aware of these 3 levels of sound at the same time. It is the essential requirement needed to play good music. The more awareness and sensitivity you have, the better musician you are. You know you are playing with good musicians when they are listening in these 3 ways as well. It's the only way to get your music to have dynamics - the only way to allow your music to breathe and for everyone to be on the same page, so to speak.

Tuning helps you become a better listener. It helps your ear to be able to distinguish between microtones - notes that are smaller than half step distances. This process over time really helps to fine-tune your listening ability. (Pun half intended.)

The only time that I really ever use an electronic tuner is when I'm playing a gig or when my guitar is so far out of tune that I just want to get a quick approximation of a tuned guitar. Usually, I'll always have to fine tune my axe when I play. Tunings even change slightly when the key that I'm playing in changes. As you progress with your instrument, you'll start to tune with harmonics, chords and other fretted notes - in essense you'll derive some sort of ritual to get your beast in "concert" or "concert pitch" which means tuned relative to 440-A.

Each guitar is different as you probably know and the intonation on every axe is different. Intonation basically refers to how well the open string pitches on a guitar line up with the fretted string pitches. When these notes are way off - your guitar won't ever get in tune no matter how hard you try. Obviously, some guitars are better than others. Tom Andersen guitars always seemed to tune very easily and stay in tune for instance. Although, no guitar's intonation is perfect. It always seems to be a "law of averages" - kind of like life I guess. You have to find some kind of compromise. That's my big gripe with electronic tuners - they don't account for a guitar's intonation and that's why they don't seem to work at times. If you have a really good guitar with close to perfect intonation and relatively new frets, an electronic tuner might actually be able to get your beast in tune without having to fine tune it.

By the way, if you can't get your axe in tune at all, put a new set of strings on it. That usually improves the situation. If it doesn't, bring your guitar to someone who knows how to fix such things. My acoustic guitar, for instance, needed to get new frets to get it back to being able to be tune. I was amazed at how much difference the new frets changed the intonation.

I encourage you to resist using an electronic tuner except when you're playing a gig or if you are doing some recording. Tune by ear. This will really help you to become a better listener. Good luck, persevere and try to keep it in tune!