Lightning Quickstart

The quick tutorial can be found here : Lightning Quick Start (PDF)

Error that you might face:

FIELD_INTEGRITY_EXCEPTION

Note that your code is something like this

<aura:application >
     <jam:hello />
</aura:application>

Note jam is namespace.In my case my namespace is unid.Replace jam with unid.

After that click Preview, you may get URL No Longer Exist--I close my browser and reopen it.It works fine.