Make sure the expiration date is still good, and the person is storing them properly. When using the condom, use it properly. Make sure it's right side out, and make sure you pinch about a half an inch at the tip of the condom to collect the semen. If a male isn't circumcised, make sure he pulls back the foreskin before rolling on the condom. Also, pinch the air bubbles out.
Air bubbles can cause the condom to break.
Then, during sexual activity, the penis definitely has to be erect, and the condom must be put on before any contact is made with the penis or vagina. When rolling the condom down the shaft, it should be done carefully and slowly, so as not to tear it. Upon withdrawal, hold the base to prevent the contents from spilling. If you're not allergic to spermicide, put a little of it on the inside of the tip of the condom, or you can also use a lubricant. That adds some sensation.