I am a heroin addict, and I'm still currently using. From my personal experience with using and shooting up, you can go about it in the safest way possible. Some pharmacies will sell clean, unopened packs of needles to anyone. Not knowing the side effects of shooting? If you do use a new, clean needle, and do not miss your vein, then the only side would be getting high... Not to glamorize it at all, but that is the truth. I have reused needles over and over again, and have had abcesses before, which require you to get them drained by a doctor if they get infected.