Inotation?!?

[hybrids_of_steel]

My inotation is way off, can anyone tell me how to fix it?

[WindowLedge]

Intonation is altered by making minute adjustments to the length of the string at the bridge. Most bridge styles (on electric guitars) have a screw for each string that allows you to move the bit that touches he string forward or back. Using a chromatic tuner, the most common way is to simply make it so that the octave (12TH fret note) is in tune with the open string.
I have my own little method where i place my fingers at the 12TH and 13TH fret (simultaneously, two fingers) and match pitches on either side of my fingers. With the gain turned up this method produces feedback when picked on the non-pickup side when it is intonated properly

If you don't understand a word of what I just said, you're probably better of taking your axe to shop.

edit: if you have a guitar with a saddle (thin white thingy; usually on acoustics) for a bridge, you should probably take it to a shop.

[Farm girl]

you can adjust it like WindowLedge said but I was told to make it so the note at the 12th fret was the same as the harmonic at the 12th fret (tune the harmonic first, then tune the 12th fret note to it)

[Cool Beans]

I HATE intonation. Evil stuff, mine still isn't sorted.

[Peg Dizzler]

It isn't as difficult as it sounds.
Window Ledge said it well; also, the 12th fret harmonic is equivalent to the string played open, so either way it makes no difference.
Like he said, it's all in the length of the string; tune your open strings, and make sure they're spot on, then fret the 12th fret of each string and see if it's in tune. If it's sharp, move the little saddle on the bridge away to make the string slightly longer. It's flat, move it towards the rest of the guitar to make the string slightly shorter. Obviously a good tuner helps in this process.

And yeah, if it's an acoustic with one big white saddle under the strings, you might as well take it to a shop since that's a whole 'nother process. Plus, if you take it to a shop and tell them you want a setup, they'll just adjust your truss rod, bridge height, and intonation all at once, as well as check your guitar for anything else that may be wrong (electronics, fret buzz, etc). So it's quite worth it, as doing all those things at once takes some practice.