Almost every very stripey chick turns out to be a boy. Some of the not stripey ones are boys too though. Very few stripies are girls but it's not impossible.
Once they get to five or six weeks the boys are a bit more red in the face and have bigger wattles and much bolder coloring as they feather up first. I can't exactly describe the way they walk but the boys have a much more confident gait. Head up, tail right up, standing as tall as a bantam can while the girls are more subdued both in color and confidence.
It's easy at five months old, the girls are scratching about, the boys are roasting over a barbeque