executive summary: check to see if it's full
I've been having this problem a lot lately, with OSX 10.9 and iTunes 11 on a 4th gen iPod Touch with iOS 6. I think there are a few contributors in my case, that seem to combine to stall it, often at "importing photos" or "preparing items" in step 8 (will stall for hours until I kill it).
One issue is that when I plug it in, iPhoto opens to copy photos off. I think the coordination between iPhoto 9.5 and iTunes may be buggy. Sometimes there are no new photos, and iPhoto doesn't offer any particular path forward, so there's no way for me to tell it I'm done with the (non-)sync. Meanwhile, iTunes seems to be waiting.
Another issue is that there are a couple photos and a couple music tracks that it has trouble moving over; these all work fine on one side or the other (ie Mac can play the audio, iPod can view the photo). I've wondered if a wipe and restore might cure this, but haven't been willing to risk this yet (worried it might fail to restore the same way it fails to sync).
These combine to make sync'ing unreliable anyway, but I think my most recent troubles were triggered by a new issue: the iPod was completely full, and iTunes didn't know this. I was tipped off when it claimed insufficient space for a 21 MB app downloaded in iOS, and I checked the iOS settings/general/usage screen to see "0 bytes" listed free. It had been filled up by me downloading podcasts to it that weren't being deleted -- I resolved this by manually deleting a bunch of them, and after a variety of sync attempts after that finally got it to complete. Even after this, iTunes thinks there is 8 GB free but the device says 4 GB, so there's a disconnect there. The way iTunes and iOS 6 handle podcasts seems clunky and is likely a factor.