If your dad was a candidate, he probably did receive a stent as part of his emergency treatment for heart attack. The most important factor of prevention of a second heart attack in the first 6-12 months after the stent is compliance with the two essential medications to prevent the stent from clotting up. One of these two medications is aspirin and the other one would be selected by his doctor. Also, his interventional cardiologist will usually determine whether he sill has other significant blockages that need to be addressed or not. A timely stress test is usually recommended by his cardiologist, if necessary.
The other aspect of preventing a second heart attack is what we call a Secondary Prevention. Basically, it involves various other medications, which vary depending on your father's other medical conditions and risks. Typically, the medications may include statins for cholesterol, Ace Inhibitors or ARB, Beta Blockers, etc.
Lifestyle modifications which, again, depend on what his own lifestyle is (i.e., smoking, weight, diet, exercise program as recommended, mental stress management, etc.).
Regular follow-ups with his cardiologist and updating loved ones for unusual, new symptoms like chest pain are all important.
With these precautions the risk of another heart attack is quite low.