How early will I be able to tell the sex of my chickens by looking at them?

[newchickenista]

I guess the subject line says it all. My chicks are 2 weeks old and I am noticing, what I think are, some differences developing amongst some of them. What I want to know is how early can you begin to see different gender characteristics develop and what characteristics do I need to look for? This is my first batch of chicks ever so the first time I'm getting to observe them develop. Hoping I have a rooster in the mix!

 

[Charm1704]

Generally the little pullets will start to feather first, where the little Roos are slower to feather, tail feathers etc....~Charm1704

 

[Dingo]

Sometimes they keep you guessing. I have 4 4-week olds that look like roosters one day then pullets then roos again.

 

[chikenscratch]

I have 10 chicks (as straight-run) and I am a new chicken owner. I have NO idea how to tell my chicks apart this early. Any input is helpful.