In Australia, we only say 'mates' in the possessive form, for example:
"My mates are down at the pub."
"His mates are all good blokes"
"They are all mates of mine"
We never say "G'day mates"!
So, here's a tip:
When speaking to one person - [COLOR=darkred]"G'day"[/COLOR], or [COLOR=darkred]"G'day mate"[/COLOR]
Plural (more than one person) - [COLOR=darkred]"G'day"[/COLOR], [COLOR=darkred]"G'day fellas"[/COLOR] (when talking to a group of men)
If there are both men and women in the group - [COLOR=darkred]"G'day"[/COLOR] or [COLOR=darkred]"G'day everyone"[/COLOR]
If you are not sure, just say [COLOR=darkred]"G'day"[/COLOR]
There an Australian song that goes:
[COLOR=blue]"G'day, g'day
And how're ya goin'?
How do ya feel, and what's yer name?
G'day, g'day, and how're ya go-oin'?
G'day, g'day, g'day, g'day"..[/COLOR]
See ya later..