To hear the "oscillation effect" Gil mentions (in full impact), a bit of distortion brings it to the fore like nothing else! Its that wow-wow- wow - wow sound that gets faster/slower depending on how similar the two notes (played at the same time) are in pitch (you want the oscillation to be as slow as possible, ultimately to be inaudible). Some guys prefer tuning with lots of distortion on, it certainly sounds more "horrible" if your tuning is slightly out of wack, plus it helps tuning with harmonics etc. Another good tuning technique.
I also like to tune in fourths, I just pluck two adjacent strings and tune the notes to create a pleasant sounding perfect fourth. When the notes sound really nice together, it automatically 'tempers' the tuning over the guitar so it sounds nicer than with a tuner.
For the B string (not a fourth up from G) I sometimes play it and the low E, and tune for a pleasant sounding perfect 5th. I dunno, tuning to different intervals is just more fun for me than tuning with unison notes - partly because its easier to tune during a song and sounds cooler (less like, umm, tuning), you can work it into riffs while playing etc. A guitarist should be constantly correcting slightly out of tune strings as they play... I hardly ever sit down and go "Oh lets tune the guitar now, its totally screwed", I just adjust tuning while playing and it stays pretty much perfect unless I break a string with a floaty bridge guitar like a strat (AHHHH! - everything is thrown out so bad you can't even finish the song!). Luckily I don't take chances like that and replace strings far before what I guesstimate their potential breaking point to be. Sometimes you get a dud string that breaks in 1 day (usually get at least 3-4 days outta them, much longer on the Les Paul (no trem, much thicker strings)). I spend too much money on strings, but the way I play neccesitates it, plus my hands seem to oxidise the strings really quickly (within half a days playing usually) to the point where a shiny new string has lost all shinyness in mere minutes. Very annoying! I wish Willy Wonka would make an everlasting guitar string!
One of the best ways to improve good tuning: new strings will make a guitar infinately easier to tune (and keep it there) than with old worn out strings. Much more consistent and predictable to deal with. If a guitar is having a hard time staying in tune, time for fresh strings.
How often do other guys need to change strings? Does your playing style/s require loads of strings or can you stretch 1 set out over weeks, even months with it still sounding good?
I just don't "get" the logic of tuning guitars to in-betweeny 1/4 tones (eg half way between Eb and E)... Surely standard semitones are small enough pitch variations to get the desired tension/tone etc, while still actually allowing you to play with other musicians (ie actually have a band), unless one is solely a bedroom guitarist, in which case it doesn't really matter, but is still kinda strange.
I suppose if you're just playing with yourself, you don't need to be in-tune to the needs of others... hang on that came out wrong