Intonation Help

Ok, I'm not exactly a "new" guitar player - however, I've never really taken lessons for over a few months, or taken it too seriously learning myself.

Here's the problem - Standard Tuning always starts to bore me, and I switch to dropped-D, and sometimes move that down 1/2 a step or a full set.

Problem - you probably guessed it already (and given the title), my intonation is now completely out of whack.

I'm going back to standard, and I'm going to try to take it seriously and learn my stuff - so I'd like to set it back. Is it easy enough to do, or should I take it in? I really don't know what it'd cost.

I have an Ibanez RG - it has the lock at the neck, and a floating bridge - I don't know if that makes a difference. I've got a key, so I can move the little things that hold the strings, back and forth. From what I recall - I need to fix it so that the length of the string from frets 1-12 and 12-to something are basically the same length right?

I was just checking my tuning and here's how it goes. Going up one fret on the bottom string I go from

E - F - F# - G (a little flat now) - G# (little more flat) - A (even more flat) - by the time I get to the 12th fret, my notes are constantly flat. My tuner says around -25cent, whatever that means - but it's pretty flat.

I can look around online and find little lessons - but I really prefer person to person, because I get better instructions and I can ask questions!

I only have a basic account on here, so I can't go to many links.

Anyway - I'm hoping it shouldn't be too hard. Any help is appreciated - if I should do it with new strings on, or without strings (a lot easier) and just measure, etc, etc. I've never really done it (although I have a basic understanding).

Another thing: when I go to where the strings go in, they are small metal clip like things. Closer to the pickups, there's that little screw type thing, when I losen it, I can move the clip back and forth that way - I assume that's what I need to fix.

Ok. Tune your guitar up all nice and good. Turn on your tuner. Play a harmonic at the 12th fret on the low E string. It should be somewhere in the general vicinity of dead-on. Now fret the low E at the 12th. Chances are it's either gonna be a little sharp or flat of whatever the harmonic was. If it's flat, you need to move the little string-holder thing (saddle? Is that what they're called?) of the E string forward towards the neck. If it's sharp, move it farther away from the neck. Now check both the harmonic and fretted note again to see if they're tuned to the same place. If not, just make another adjustment. Keep doing this until the fretted note and harmonic are one and the same. Now do this for the other 5 strings.

To help you remember, just think of the 3 F's: If the Fretted note is Flat, move it Forward.

I hope that helps.

Thanks for the suggestion.

I can't seem to get it to work no matter what I do. The harmonic always seems to be flat - no matter how far forward I move the thingy, or how far back. The other notes change around - but the harmonic just always seems flat.

Maybe I'll have to take it in.

If the harmonic is flat, you might be just hitting it in the wrong spot. Move your finger over until the harmonic shows up as in tune. This is the spot you have to work from.

I always use an electronic tuner - personal choice

Actually, using a harmonic on the 12th fret isn't the most accurate way to do it.
You should play the note at the 12th fret and compare that to the open tuning instead. That way you'd be taking into acount your normal finger pressure on the upper frets rather than tuning the open string to the open intonation.