This is a huge topic, as there are countless ways to get cool tone (and countless ways to get bad tone). I have a small collection of great tube amps, pedals, and even some modeling stuff that all sounds pretty damn good, so I could ramble on about this topic from various standpoints.
Now, I know we all probably agree that if we can afford a good tube amp, then we've gotten to a great place as far as getting good tone goes. So, one of the coolest discoveries I've come up with is using an Electro Harmonix Black Finger tube compressor pedal on your tube amp for garage crunch.
A friend of mine was selling one really cheap, so I figured I'd buy it to try out and then flip it shortly afterwards to make a few extra bucks. But, once I started using it I fell in love with it. When using a tube compressor pedal with a tube amp, it not only compresses and gives you a fat tone, but it also gives you a naturally over-driven tube tone without actually using an overdrive pedal or switching to the drive channel on the amp. Very simple, very effective.
What I'm trying to say is: you could have a tube amp on the clean channel, put the tube compressor on it, and you'll get a nice and punchy/solid tube overdrive that isn't too static-y or distorted and it really sounds good for garage style tone.
Try it out and let me know what you think.