steps on to have a glowing object on mouse over.

For GUI objects, see this answer:

http://answers.unity3d.com/questions/8217/mouseover-detection

For 3D objects see this answer:

http://answers.unity3d.com/questions/35784/change-mouse-cursor-on-mouseover

http://answers.unity3d.com/questions/10591/text-box-pop-up-on-mouseover

It basically comes down to this script:

http://unity3d.com/support/documentation/ScriptReference/MonoBehaviour.OnMouseEnter.html

If you are not familiar with how to use the scripting side of Unity, I'd recommend running through a bunch of tutorials to buff up your knowledge first.