My 92 year old father has bleeding problems. What precautions should he take before oral surgery to remove infected teeth ?

Thorough Evaluation. A thorough consultation needs to be performed by the surgeon who will be performing the surgery for your father. Your surgeon will need to have a complete medical history on your father as well as a complete list of all medications, prescribed as well as overt the counter medications taken by your father so that the surgeon can provide you with preoperative instructions.
See Oral Surgeon. See the oral surgeon for consultation before treatment is planned. They will contact your father's physician and develop the best and safest plan for treatment. Normal to plan for this.
Definitely Depends. Bleeding disorders like hemophelia and other clotting deficiencies can impact bleeding to varying levels. Blood thinners like coumadin/heparin/lovenox also have a big impact with implications on dental treatment. Others like Plavix (clopidogrel) have a lesser impact because they work differently. Also, the extent of the surgery is important to consider as well. Consult with the doctor performing the surgery.
It depends. On the exact nature of the bleeding problems. He may have a genetic bleeding problem, or it could be due to anti-coagulant therapy such as Coumadin (warfarin) or aspirin. Often, we do not have to take patients off of these therapies for a few simple extractions. Recent research has proven this. It is best to see an oral surgeon to discuss the best approach.
Antibacterial rinse . Try an antibacterial rinse containing Chlorhexidine to reduce inflammation and bleeding prior to extractions. Also discontinue Aspirin if taken daily.
Medical clearance. Often it will be necessary to get medical clearance from the primary care physician for dental extractions that may involve testing for clotting factors.