DK,

Practice as much as you possibly can, when ever you can, if you really want to improve. I typically leave a guitar in the bedroom, livingroom and of course by the computer (I ain't rich...LOL...they're all cheap guitars, trust me), that way you've always got one nearby and waiting to be played. Try playing along with the music on the TV or just whatever you happen to hear. Even without an amp, you can still do a lot of good by just noodling away on an unplugged electric while you're hanging out watching TV or whatever.

As far as the callouses go...I play all the time & I really don't have any at all to speak of. You wouldn't really look at my finger tips & go "Whoa...those are some serious callouses!"...LOL In fact just looking at them & feeling them, there is almost no difference from my right hand. It's just at some point, after all the hours of playing/practicing....they stopped hurting from excessive playing. Like most aspects of music/guitar playing, it's going to be a little different for everyone out there.

Best of luck to ya,
Don