Chest Pain The first and most obvious sign is chest pain. It may be radiating down your left side (jaw/arm). It is generally described as a crushing pain. This symptom is less likely to occur for women or people with diabetes. If the chest pain is not relieved by resting (i.e. sitting down), it points towards a heart attack.
Shortness of Breath As a body attempts to bring more oxygen into the body faster (because your heart isnt perfusing efficiently anymore), breathing will become faster and more shallow.
Pulse - Rapid, Weak You should take your pulse a few times a year to get a baseline of what it's normally like. During a heart attack, it can become faster and weaker. However, this is relative - your pulse may normally be weak. This is why it is important to have a baseline.
Nausea, Dizzyness, Sweating, Weakness These physical symptoms by themselves are usually not a concern (they happen with many sorts of illness really) but in combination with the above can be a warning sign.
In any discussion about heart attacks, it's important for you to understand the risk factors: http://www.mayoclinic.org/diseases-conditions/heart-attack/b...
If you're high risk and are suffering from the above symptoms, its always advisable to err on the side of caution and call the emergency services. In fact, if you're at all worried, just call.
There are some things you can do to help yourself during a heart attack: 1) Call emergency services. 2) Make sure emergency services can access you, especially if you're on your own. Unlock door, etc. 3) Half sitting position. Place your back up against a wall and sit with your knees raised. 4) Take an aspirin. This will thin your blood and relieve pressure on your heart. 5) Try control your breathing. 6) Try not to worry (yeah, I know, this is a hard one).
Source: EMT (Emergency Medical Technician) with voluntary ambulance services.