We guitarists are notorious for spending vast amounts of time, effort, and money in our quest for that elusive Holy Grail of perfect tone. An entire industry exists solely to supply the tools for our insatiable appetite for angelic overtones, crisp mids, sparkling highs, and thundering lows.
While I am not immune from the Siren's call of the local music store, I want to propose a foundational idea that may have eluded some of us on our tone quest.
Can you hear the tone you want in your head, when you are nowhere near a guitar?
What I mean is this. If you can't imagine/hear the tone you want in your mind before you go twisting knobs, trying different strings, replacing speakers, swapping out pickups, etc., then the chances of you finding "that" sound are pretty slim. You may stumble upon tones you like, but you will have a difficult time finding your "voice" on the guitar if you can't define what it sounds like in your mind.
Try this experiment with an unplugged acoustic guitar. Get it in your hands and play on it for a few minutes. It may sound good, it may sound cheap and bad. Doesn't matter. Next, close your eyes and imagine/pretend that guitar is the best sounding acoustic in the world - one that creates "the" tone you hear in your mind as your perfect sound. Now play that guitar, eyes closed, imagining that awesome tone is there.
You may not actually achieve tone Nirvana this way, but you should see a marked improvement in the sound you are getting out of that guitar. Why? Because you were carrying that sound inside you, and what you carry inside comes out thru your hands and playing.
The same principle holds true for an electric rig. Have you ever had another player take a turn on your rig and get a tone out of it that you couldn't get? That's because he/she was carrying a different tone inside of them, and that affected their playing technique - their hands.
So before you run out and buy that $4,000 amp to try to improve your tone, try envisioning "the" tone you want to create in your mind. If you own that tone inside of you, it will guide not only your hands as you are playing, but also the knobs you are twisting on the amps and effects pedals you currently own.