I choose my tracks for the show, then take note on the posts; which songs have the longest instrumental intros. I plan my airbreaks around those so that I can create a smooth transition into the music. What helps more, though, it taking note of the outros to songs, whether they are cold or fades, or natural endings. You can cue up the beginning of a track pretty easy, but the end is more difficult.
Listener interaction is key to building a memorable show and creating P-1's. There are no "stupid requests," but you can always guide listeners to something else that may be more appropriate. Answering the phone line/responding to emails should be taken more like customer service than an arrogant dude on a podium. As a DJ, it's pretty easy to be the latter.
I always try to frontsell, vs backselling. This way, people who tune in mid-way can still carry on and it keeps people listening through stop-sets. The recording/podcast/playlist posting is for the people who want to check out what has already happened. In the same light, I only talk about gigs that are coming up, and not past ones. People can't attend a show that has already happened, but your 30-45 second airbreak could bring in a few more ticket sales to next week's gig.
In a music related show, your airbreaks should not deter from your subject. Short and sweet. And don't try to overshadow the the music. Play music you are stoked to play, listeners can hear it!
Also, when having a co-host, continue to talk "TO THE LISTENER" and not "to your cohost." Radio is live, and radio is interactive, keep the audience involved.