How to...?

[woodelf]

I don't have perfect pitch and am only an average guitarist anyway, so how do I recognise whether a song I hear is in standard tuning or in an alternate tuning, as in folk or blues for example...is there a definitive way to do this?...Ta Muchly.

[Scarlett]

Are you saying that you can do this, or that you want to be able to do this?

[Scarlett]

Assuming you want to do this..
As a guitarist you should try and test yourself. Get someone to play some chords- A, Em, C, D, B7 etc all in first position. See if you can identify the chords. Because the chords all have a different "sound" unlike piano, due to the different fingering, and what notes are at the top of the chord etc.
Eventually you will be able to hear what chords are being played in songs- this is how people work songs out by ear. It is usually only a matter of practice and your ear getting used to the sounds on the chords.
Then you will try and work out a song one day and none of your chords sound accurate- this is when you will find that an alternate tuning has been used. The bottom E string will sound different- looser and lower. You can also hear from the fret noise whether the player is moving higher up the fret board or staying put!
It usually just comes with practice as your ear gets used to the sound of "normal" chords compared with other tunings.