If you've ever attempted to sex a chicken, you probably understand how difficult it can be. Regardless of the method you try, it takes a really keen eye to be able to tell the difference amongst cockerels and pullets. Even if you buy from a breeder, there is the possibility that they, too, will sometimes make a mistake. Best intentions aside, sexing chicks is tough, and sometimes you wind up with a cockerel when there is only room in your coop for pullets. Then what?
Since having more than one cockerel will eventually result in an assertion of dominance as they mature and become adult roosters, there will come a time when you will have a fight on your hands. This could lead to an injured or even dead rooster and it is humane to avoid giving such behaviors a chance to occur. At this point, you basically have two choices: cull one (or more, depending on how many you have) rooster or rehome him.
Culling is an option often exercised by those who raise birds for meat. Not everyone is comfortable with culling, however, especially if you consider your chickens to be part of the family. In the even that you feel bonded to your rooster, it might be hard to toss him in the stew pot and eat him for dinner. Being unable to cull and possibly eat an animal is a respectable decision, but you still need an alternative to recurring rooster fights. If culling is out, rehoming is the next possibility to consider.
When rehoming a rooster, you need to be honest with yourself about the fate he might meet. Even if you cannot eat your rooster, that does not mean someone else also cannot eat him. If your problem is one of you not being able to cull him but you are not necessarily opposed to someone else doing it, then you may be successful at rehoming your rooster. However, if you are strictly opposed to anyone consuming your rooster and wish for him to live out his days free ranging and mating with hens, finding a home for that rooster will be a little more difficult. The best course of action is to ask around and see if someone is in need of a rooster in hopes you can be put in touch with that person. Be advised, however, that various internet classifieds are often filled with adds for free roosters who's owners hope they can go live out their days happily on a farm and not a plate so you will likely encounter competition on the rooster rehoming market.
Lastly, you may be able to place roosters through your local feed store, especially if they were purchased there. Some feed stores will take roosters and pass them on to people who will either home or consume them. This generally applies to small businesses, however; do not put all your eggs in one basket when it comes to a big box type feed store to taking your cockerels or roosters back in hopes of finding them the perfect home.
When it comes to making future purchases that do not include cockerels, buying sexed chicks is your best bet. Although one occasionally slips through, chances are that your order will include only what you requested. Another option is a sex-link, which is a cross breed in which pullets are certain colors with cockerels being of other colors. Sex-links eliminate the guesswork from the get-go. You can also opt for a straight run but the odds there are worst of all with a 50% possibility of a cockerel.
Whichever means of sexing you choose, just keep in mind that nothing is ever truly certain and mistakes happen. Even if you get a guarantee, all that means is that the situation will be made right, not that it is sure not to be wrong in the first place. If you do not have room for a rooster, be it because you already have one or due to backyard chicken ordinances not allowing one, hatching a plan for his removal ahead of time is going to be in your best interests as well as his.