Safer sex is the best and most effective way to prevent an HIV transmission and other sexually transmitted infections.
Established safer sex rules, which are still valid today are:
when you fuck someone or you get fucked always use a condom. When you go down on someone don’t let him come in your mouth. You can kiss and caress to your heart's content.
It is worth pointing out that safer sex is never 100% safe either. For example, condoms can break or slip off. However, this risk can be greatly reduced by knowing how to use a condom correctly and by practising how to use it. You can find out more about this under "Condoms protect".
But nowadays safer sex is also much more than just the use of condoms, because under certain conditions a successful HIV therapy can also protect against HIV. Anything you need to know about "Treatment as Prevention" is explained here.
If something does go wrong when you have safer sex, there is the possibility of a short-term antiretroviral treatment to reduce the probability of an HIV infection. You can find everything about the so-called Post-Exposure Prophylaxis under „PEP“.
Another HIV prevention strategy is Pre-Exposure Prophylaxis, or PrEP for short. It can help protect against an HIV infection by regularly taking HIV medication. Under „PrEP“ you can find everything you need to know about this and also the current debate.