It may be 123,12 or 12,123 depending on the tune.
(often written as 3+2 or 2+3 respectively

Take Five is 3+2
The Gas Almost Works (John Kirkpatrick) is 2+3
The Weaver and Factory Maid changes mid tune!

Balkan dance tunes are a bit different - often the time sig is in quavers (half notes) so Pajdusko Horo (5/8) is 2+3 but it's really 1+1½ - short and long beats.

As to identifying timing - it's how many evenly-timed pulses you can count between strong beats. The first beat of the bar tends to be the strong beat. Easier said than done - you need somebody to show you, with typical tunes, so you get the feel for it. Sometimes the things that you count come a bit fast! (anything with 8 instead of 4 on the bottom of the time signature, for example)

Anahata