You can contract HIV by having sexual intercourse with someone who has it already (condoms reduce the likelihood of catching HIV from someone through sex to nearly zero, but it's still possible), by being born to HIV-positive parents, or by having blood-to-blood contact with someone who has it already (I had to get tested last year because I got someone's blood in my mouth by accident).
Through oral sex anal sex vaginal sex breast milk sharing needles if you had a open cut an they had a open cut n was bleeding an put the blood in your cut you cud get. Bodily fluilds.. Not spit if you drank 5gallon of there spit in 1day you could.
Virulence of the virus and health of the person's immune system prior to infection will be a factor. For example malnutrition or heroin addiction would compromise the immune system and therefore a much lower viral dose would produce infection. Saliva and sweat would thereby become possible sources of infection, and, somewhat controversially, new born babies are at risk if handled by an infected person. New born babies have a high prevalance of Langerhans cells in the skin and it is via Langerhans cells HIV infects the body. In South Africa there have been a number of cases of babies becoming so infected. (Langerhans cells are mobile immune system cells and it is via the Langerhans cells of the sexual organs or colon that HIV is mostly acquired)
Oral sex, anel sex. Vagail sex open cut with blood involved. All bloodly fuilds
Anytime the carriers blood or bodily fluids (excluding saliva) come into contact with another persons internal systems it can be contracted. So any kind of sexual actions you can imagine, and sharing of hypodermic needles.