I don't mean standing over the bath or dripping into the kitchen sink.
I've always gone for site A (disclaimer, I've just done my third fingerprick test, so not a huge amount of experience), when I give blood that's where they prick you to check your haemoglobin. It just seemed 'right'. I've always managed to fill the tubes but it's taken several fingers and a bit of effort.
My daughter did a test the other month and she pointed out site B and that there's a vein running down there (visible on her, not on me).
Anyway, I did my test yesterday, made sure to drink plenty on Sunday, a glass of water when I got up, short run to raise the heart rate, hand in a sink of hot water to get the blood going, pricked finger at site A, twisted the lancet before removing it, and got a paltry dribble out of it before it stopped flowing. At that point I remembered what daughter said and went for site B on the second finger. Much more blood, bigger droplets and also darker blood, venous rather than arterial maybe??? Anyway, 5 drops was sufficient to get to the 0.4ml mark on the tube, another 3 drops and it was full, on to the second tube, again 8 drops filled it quite easily. All over and done in about a minute.
I thought I'd share, though I may be late to the party and you've all been doing it like this for years. But if anyone struggles with squeezing blood out of their fingers it may help.