American Idol and all the reality TV singing shows have been super hot for years now. While we all love to feel the emotion and get wrapped up in the performance, as singing students these shows give you a wonderful opportunity to watch people sing well...or not so well.
On the positive side, if you can see their bellies, focus on their breathing and support. Do their chests stay still during breathing? What tricks are they using to effectively use resonance -- is anyone wrinkling up their nose or snarling their lips up a little? Those are two effective resonance tricks to watch out for. Also, on high notes, are the singers bending their knees a little? Another great trick!
Some things that you can watch for that aren't so good are chins lifting up in the air for high notes (listen and you can hear the strain), lots of shoulder movement while breathing (bad support), and scrunched eyebrows (impedes resonance and adds unnecessary tension).
Listen to how the techniques, tricks, and mistakes affect their vocal tone. You'll be a better singer for it!