Dude, Pandora. Take the time to set yourself up a radio station properly: start by picking the most prototypical song you can think of in the style that you want to hear more of. Let's say you want an entire radio station that sounds like Social Distortion's "Ball and Chain" -- you click on "create a new station", enter "Ball and Chain", scroll down 'til you get to the Social Distortion choice, then click it. Voila, you're done.
Well, not quite -- you're well on your way, and if that's all you did, you would probably be pretty happy, but you should do more.
As songs play, click the thumbs-up or thumbs-down icons -- only if you really like or really hate the song (or more accurately, "really think that song is appropriate for this radio station", or "really think it is inappropriate"). Also, while they're playing, if you can think of any other songs of a similar vein, then here's what you do:
Left-click on the down triangle next to "ball and chain radio", and click "add more music to this radio station";
Enter other songs as you did similarly.
Also, if you screw up, you can always left-click->edit, and remove added songs, and songs you've "approved" or "disapproved".
Have fun! Experiment.
Oh, and apparently -- Slim Devices and Pandora have some sort of agreement, and the whole interface is somehow compatible with the transporter. So if you like what you hear, you should look into that. You can approve and disapprove straight from the remote.