Determining the sex of baby chickens can be very important for some people. Those living in cities with ordinances regarding roosters and sound restrictions need to deal with their male population and move elsewhere so they don't get into trouble. Farmers also need to separate the sexes as soon as possible to begin socializing them in their specific roles. However sexing baby chickens isn't a simple "look under the feathers" job. In fact it usually takes a professional to correctly identify gender with a high level of certainty.
Check the chicken's vent (anus). The sexual organs are located inside the vent. There are more than 15 shapes of copulatory organs so you will need to correctly identify the shape, which can be difficult when it is so small in the first few weeks or months of life.
Examine the feathers. Longer covert feathers are typical of males while longer primary feathers are commonly seen in females. Some species have specific types of feathers, which someone with a trained eye might be able to spot such as rounded feather tips which identify a female chick. This technique is known as feather sexing.
Look at the coloring of the feathers, beak and sometimes right at hatching. Different species have identifying color characteristics, which can identify gender.
Hire an expert to sex your chickens. Find someone who has been trained in the various methods and can assure a high percentage of accuracy.
chicken image by Sergey Goruppa from Fotolia.com