well, im doing only quad shots and man, i usually dont even feel the needle entering, and even injecting the liquid is usually painless....
for the little experience i have now (lol) you have to go to upper-outer thigh...every time i got too low or too centered on the leg, the pain was a lot bigger....
I just f*cked up one shot, where i did more or less on the wrong spot and then hit a vein....i got nervous, but looked for another spot and hit a vein again!!!!! man, i was shaking like hell, but tried once again....I didnt hit a vein, but it was the most painfull shot i ever had...the needle was like tearing my flesh apart....it hurted like hell, and if i touched the spot where i injected, i would feel pain on almost all the side of my leg for more or less 2 weeks....on this time i just used shot on the right side, and i think i started to do it better because i never had any problem since