Number 4 is something that is quite dangerous but it does cause insta-vascularity. When you close your nose and mouth and push hard, it increases your blood pressure – up to 300%. Its like plugging the end of a hose and turning the water on, the hose swells up bigger. People often hold their breath and push hard when posing to make their veins “pop”. Trouble is, increasing the pressure in any piping makes it more likely to spring a leak – in a hose or in your veins. If a vein ruptures at the wrong place in an eye, you can go blind. Bodybuilders who hold their breath while doing big exercises like squats, deadlifts, or bench press often get red eye – the whites of their eyes turn blood red. This is caused by small blood vessles rupturing in their eye and should be a warning to them that they need to change their ways. If a vein ruptures in the brain, its far serious and can cause death. The higher the pressure, the more likely a blood vessel will burst. Please don’t hold your breath! ( Read about the Valsalva Maneuver )
3. I’m a hairy dude, and I have Irish, Swedish and Persian blood. My dad was a soldier, state trooper, prison guard and boxer. He was absolutely jacked-up with muscle. His forearms alone were the size of Popeye’s. However, aside from his hands, he didn’t have that veiny look. And I don’t either. I spend hours in the gym, and I get jacked up with hard muscle, though I never get a six pack, and I have trouble losing belly fat around the navel and on my lower back. I do dead lifts until my sciatic flips out. I’m a tall, narrow-boned guy that laments about his thin wrists and fingers. Anyway, what gives? More celery, vitamin C and weight training will do the trick?
Vascularity is enhanced by extremely low body fat (usually below 10%) and low retained water, as well as the muscle engorgement ("pump") and venous distension accentuated by the vigorous flexing and potentially hazardous Valsalva effect which characterize competitive posing. Genetics and androgenic hormones  will affect vascularity, as will ambient temperature. (And although some bodybuilders develop arterial hypertension from performance-enhancing substances and practices, "high" venous pressure — being an order of magnitude lower than that of arteries  — neither causes nor is caused by vascularity.) Some bodybuilders use topical vasodilators to increase blood flow to the skin as well. Although historically controversial,  nowadays vascularity is a highly-sought-after aesthetic for many male bodybuilders,  but less so for female bodybuilders  where the target aesthetic is relatively more towards aesthetic symmetry than extreme development.