Simple Interrupt

I have a RFID Reader/Writer module that I am attempting to read the ID number of a transponder tag with.
When a valid transponder is seen by the RFID module, an output is pulled LOW.
I have this output connected to Pin 10 of the Arduino UNO.
When Pin 10 goes low, I must send a "read" command to the module.
My question is:
How do I constantly monitor Pin 10 to establish its state (High/Low)
If I use Pin 2 the interrupt on the ATMEGA328, how would I implement this?
Many Thanks

When a valid transponder is seen by the RFID module, an output is pulled LOW.

For how long?

How do I constantly monitor Pin 10 to establish its state (High/Low)

What else is the Arduino doing? Polling may be enough, depending on how often you poll and how long the pin is LOW.

If I use Pin 2 the interrupt on the ATMEGA328, how would I implement this?

The usual way? Use attachInterrupt to define what function to be called when the pin is FALLING to LOW.

In that function, be fast - no serial input/output, no delay()s.

robcole:
I have this output connected to Pin 10 ... If I use Pin 2 the interrupt on the ATMEGA328, how would I implement this?

Connect the output to pin 2?

robcole:
I have a RFID Reader/Writer module that I am attempting to read the ID number of a transponder tag with.

Which module? Link to datasheet?

The module I am using is RWD-QT datasheet: http://www.ibtechnology.co.uk/pdf/RWD_QT.PDF