Welcome to LiveATC.
Plane Finder or Flight24? - I would suggest you start with Plane Finder. It is easy to use and will provide you the basic information you want.
Flight24 is, in my opinion, a better flight following site, but unless you subscribe, (last I looked was around $36.00 US, per year) they have
a 30 minute view time and then you have to reload the page. No big deal, just an inconvenience. You do get more information with the year
subscription and you may want the extra features. They do offer a 7-day free trial, if you are interested, before subscribing.
For an airport, I would suggest you go to EINN (Shannon, Ireland), and monitor it. I really don't have much info on other European airports,
but that is a place you can start at.
Enjoy LiveATC