Once the needle is in, just remember to inject slowly and pull the needle out a little bit after inserting it at least an inch.
i dont agree with this as you'll probably be using 1" or 1.5" needles. pulling a 1" needle 1" out, well that'll leave you without a needle in you

. pulling a 1.5" need le 1" out, well that just wont do because you want to go deep into the muscle.
get some needles.
leave the protective cap on the needle!! now practice with it. you'll want your hand positioned on the syringe so that the needle will not get completely buried. you'll always want to see a little bit of metal. 1/8" or even 1/4". dont hold the needle like a dagger that you're trying to kill a pig with. hold it firmly but gently.
now, we'll be doing quad shots as thats the easiest, i feel, for a newbie. stand straight at attention with palms at your side(it helps if your pants are down). the area that your palm covers is the area you want to shoot. now sit down. you could leave your palm on your leg as you sit so you remember the site. so now your quad is horizontal to the floor. disect your leg in two...top and bottom. good. now forget the bottom. all you see is the top half. now disect that again. so now you have an upper top half and a lower top half. you want to shoot in between. once you poke, hold the syringe with one hand, and pull back on the plunger just a bit. if you see air bubbles, proceed with injecting sloooowly. about 15 seconds per cc. if you see blood when you pull out, remove pin and hit a slightly different spot.
now, other than sterilty, you're all done

! simple...no?
MAKE SURE YOU KNOW AND FOLLOW PROPER STERILE PROCEDURES!
as for the mental part...there is no pain. maybe a slight pinch....maybe. dont put the needle against your skin and try to slowly break through. push it in with the right amount of force from the get go. so see...we just did it in make belief land. now all you have to do is shoot the same way in your real world.
believe all of us that have said we were nervous...scared shit. most of these guys, me included, get so used to it, that we actually look forward to shooting. and if you shoot...this chick will blow you

.
have a nice day