I use top of my thighs cause I have rolling veins & very small veins in my arms & it's a nightmare. If you put a flashlight on it, you can see the outline of veins in your legs. If its super dark, close to the surface so short needle is best. Its so much easier for me this way. Plus you have both hands this way & way less chance of someone seeing marks. Rotating where you hit is key. If you hit somewhere dont use the same spot for 2 or 3 days so it can properly heal. If you have a sweet spot, thats guaranteed easy to hit, I wait to use it til I have to hurry before people come or you gotta leave. That was best advice I got. Lol Definitely stay hydrated & calm. If you get agitated it never works, set it down a couple minutes & calm down then try again. My rule is if I dont get it by 3rd try, I go down a large glass of water, wait 20 min or so & 95% of the time, when I try again, its easy. Hope that helps!