i think My Best will do great as a single.. 
Maybe an extended version. Anything under 3:30 would be hard to hold a listener's attention.
Actually, studies show that the average human can only pay attention to music for 3 minutes, otherwise they tune out. That's why "radio edits" of songs are generally shorter than album versions.
I think whilst its not my favourite song on the album, Hands On Me would be a good second single. For a start its exactly 3 minutes, and it has a really catchy chorus which is singable and therefore more appealing to an audience. The hook of "Hands On Me" is a bit provocative as well, which I could so see radio stations introducting with a bit of humour..."Vanessa Carlton wants you to put your hands on her.."
I think My Best is a nice song, but the chorus isn't catchy enough or clear enough, so therefore the audience on first-listen would find it hard to like as it does not have clear repition of lyrics and music (ie a chorus). If things aren't repeated, then too many musical ideas hit the listener on the first listen and they can't connect with the song. Radio stations don't play songs unless they are going to keep a listener listening to their station. This same thing applys with "Come Undone" - chorus isn't defined enough in the song.
Hit song = catchy and defined chorus. This is one of the reasons I think nolita fairytale is struggling as it goes to the pre-chorus ("Take away my record deal..") yet the chorus is one line ("I've found some kind of fairytale") and then it goes back to the verse. Repetition is necessary to sustain interest in a listener that isn't aware of the talent V possesses.
In summary, HANDS ON ME
