Here are the warning signs from the American Heart Association:

Heart Attack Warning Signs

Don't wait to get help if you experience any of these heart attack warning signs. Although some heart attacks are sudden and intense, most start slowly, with mild pain or discomfort. Pay attention to your body - and call 911 if you feel:

• Chest discomfort. Most heart attacks involve discomfort in the center of the chest that lasts more than a few minutes, or that goes away and comes back. It can feel like uncomfortable pressure, squeezing, fullness or pain. Discomfort in other areas of the upper body. Symptoms can include pain or discomfort in one or both arms, the back, neck, jaw or stomach.
• Discomfort in other areas of the upper body. Symptoms can include pain or discomfort in one or both arms, the back, neck, jaw or stomach.
• Shortness of breath with or without chest discomfort.
• Other signs may include breaking out in a cold sweat, nausea or lightheadedness.

Symtomps Vary Between Men and Women

As with men, women's most common heart attack symptom is chest pain or discomfort. But women are somewhat more likely than men to experience some of the other common symptoms, particularly shortness of breath, nausea/vomiting, and back or jaw pain.

More Information:

American Heart Association: Heart Attack, Stroke and Cardiac Arrest Warning Signs (view in PDF)
National Heart, Lung, and Blood Institute: Heart Attack