Suppose a common situation with a vampire occurs. They're short of blood, you want to save them, you need to deliver a moderate amount of blood to them to revive them but you don't want to be massively hurt or to injure something that won't heal. You have a knife, not modern medical equipment.
How do you give them your blood? There are some obvious answers like let them bite your neck, but that would presumably have a risk of them ripping open your jugular. I've seen people cut open their palm on tv, but that looks really painful and doesn't give much blood. If you had time you could rig up medical equipment, but this is for spontaneous situations.
Where is the best location to get blood to feed the vampire at a decent speed which minimizes pain and long term damage to the human involved?