From this site which sums them up well.
http://fionnaschooks.webs.com/araucanahistorystandards.htm
Sexing Araucanas:
Notoriously difficult to sex, Araucanas have a small comb and hardly any wattles - indicators often used to sex other breeds. Males mature at irregular ages - they can be sprouting tail feathers and crowing very early, or very late, after you have sworn they were a hen for months.
Some indicators could be:
Longer pin-feathers in female chicks compared to males between one to three days old.
At about 5 weeks the comb of males will enlarge and redden a week or two before females do (but then they even out again and this window is lost).
Males will grow the thin, shiny, pointed feathers in the saddle at maybe two or three months old - often these are coming through at six weeks. This is the best definite indicator for males. It doesn't mean that all the ones who haven't grown them yet are girls!
After two or three months of age a males longest tail feathers (sickles) will start to lengthen and curl over. Hens tail feathers remain straight.
Males will crow.
Females will lay eggs.
(Sometimes it really does take this long to be sure.)
Out of interest how old do you think you can tell with araucanas
