HIV transmission occurs most commonly during intimate sexual contact with an infected person, including genital, anal, and oral sex. The virus is present in the infected person's semen or vaginal fluids. During sexual intercourse, the virus gains access to the bloodstream of the uninfected person by passing through openings in the mucous membrane-the protective tissue layer that lines the mouth, vagina, and rectum-and through breaks in the skin of the penis.
In the United States and Canada, HIV is most commonly transmitted during sex between homosexual men, but the incidence of HIV transmission between heterosexual men and women has rapidly increased. In most other parts of the world, HIV is most commonly transmitted through heterosexual sex.
From sex, from having open wounds in contact with their blood (ie. in car accident) and I know you can get hepatitis from sharing a toothbrush and straw/note from snorting but I'm not sure about aids. It used to be possible to get it from blood transfusions but they check the blood these days. HIV can be transmitted by unprotected oral, anal, or vaginal sex with an infected person, sharing needles for drug use with an infected person, and it can be transmitted from a mother to her child during birth or breastfeeding.
Because all donated blood is tested thoroughly before use, HIV infection through blood transfusion is extremely rare. HIV is NOT transmitted by casual contact, and it is NOT transmitted by saliva. The only time that kissing an infected person would be a risk is if you both have bleeding gums or open wounds in your mouths. Basically, you can touch, hug, or even kiss someone who is infected, and not get infected yourself. You can contract aids many ways other than using a dirty needle. If you come in contact with someone's body fluids (blood, saliva, semen and so on) and it is introduced to your immune system either through eyes,mouth,nose & cuts. also during sex it is introduced to your immune system. That's about the endless ways to contract it. Best advice I can give is not to go playing in someone else's body fluids!
If you use an infected persons needle or have any of their blood in contact with your blood or an open wound, having sexual intercourse, having oral sex, breastfeeding, and childbirth will usually transport it to the child from the infected mother. Unprotected sex, Kissing with saliva transfer, blood transfusion. Any transfer of bodily fluids. I believe having sex, or getting a blood transfusion from an infected person. Sex, spit, breast milk, blood and prolonged eye contact. You can't get hiv/aids through kissing derr.