Welcome to the LiveATC community, Zermatt83!
Anyways, buying a scanner isn't too big of a task, but I remember being in your shoes not long ago. I posted this in response to a very similar question only a few weeks ago... for your reference, the full thread can be found at:http://www.liveatc.net/forum/viewtopic.php?t=1263
Here is what I looked out for when I was buying:
* Reviews online are always helpful, such as eHam.net
* AIR frequencies are required (108-136MHz) - some don't have it!
* Portable... for me this meant handheld
Detachable/Removable antennas are pretty standard with the BNC connector.
If you're at the airport observing, you should be fine. If you're further away, an external antenna is recommended. There are many other threads on antennas. Goodluck and have fun!