It seems the first place vampires go for blood is raw meat. Only give blood from raw meat to those under the age of 18. When the individual turns 18, he/she will have a greater hunger for blood and will be mature enough mentally to obtain it responsibly.
Give him/her only cow blood because pig blood can contain trichinosis.
Blood should be obtained by buying it from a very clean butcher shoppe, preferably the butcher at the meat counter of a chain grocery store [they will be very clean to uphold their integrity]. Just tell the butcher you want to purchase beef blood for making blood pudding or blood sausage.
I recommend giving the individual under 18 years old blood in the form of a recipe that calls for blood before feeding him/her raw blood to see if the cooked blood helps, because cooked blood is safer for consumption.
For blood-drinkers over the age of 18, here are ways of obtaining blood...
A. Sucking on a part of the body until blood comes out
B. Biting an individual on the lips because the mouth is the fastest healing part of the body
C. Using mouthwash before biting an individual to prevent infection
D. Using lancets intended for diabetics
E. Obtaining blood through sadomasochistic practices because the anticipation of the pain in that circumstance would be enjoyable for the other participant as well
F. Drinking menstrual blood
G. Drinking blood psychically