Avoid people and places that will expose you to illness or bacteria.
 

Wash your hands often. Keep your unwashed hands away from ALL mucous membranes, especially the nose, eyes, and mouth. You are more likely to catch a cold through your nose than your mouth because saliva contains a lot of bacteria-killing enzymes.
 

Clean often.  One thing that I do that surprises a lot of people is "lysoling" the phone and the steering wheel of your car. Lots of germs there. Plenty of rest, juice, washing hands at appropriate times, etc. I also carry antibiotic hand wash but I don't use it too often - it's not supposed to be that good for you but in emergencies when I have been out (subway, etc) and can't wash hand, I'll use it. -Ronnie in CT
 

See Diet for Immunosuppressed Patients
Patients receiving chemotherapy and radiotherapy may have compromised immunity.
 

Do not purchase products older than the pull date. Read labels.
 

Store and handle properly foods to avoid food-related infections and illness. 
 

Avoid moldy, spoiled and outdated food products.
 

Replace dish and face towels after each use.
 

Thoroughly wash produce; cooking fruits and vegetables is best. Use vinegar to clean vegetables, and/or mild soap.
 

Beware of foods that have been "double-dipped."
 

Ask your doctor about Neupogen^® for treatment of prevention of low white counts. See Restorative biologics