Want to see the most and eat good in 24 hours, any recommendation? Also if there is any seasonal show or art exhibition going on right now :)
Get up early! You can watch the sunrise over the Western Wall, when the light and the many things to see are more than you can process if you don't take the time to let it in.
Also, it is simply great to walk through the old town before all the shops are openend. When you return when business has kicked off you won't recognise anything anymore!
Further, the Wikitravel page on Jerusalem will give good advice on places you can visit. Not for the fainthearted, but not to be missed (!) is a visit to the Holocaust museum: Yad Vashem. It is absolutely breathtaking. Even though I was raised in Netherlands and therefore are well educated Which horrors took place in 1939-1945, it is absolutely overwelming to witness the telling of these black pages of our history. It's not fun, but it is worth a visit even though you have 24hrs! about 5 years ago