The second way is to not have s.e.x with anyone. Since people are carriers of AIDS and HIV, avoid the transmission source.
Not only will you have to avoid s.e.x, but you’ll also have to avoid possible contamination through blood, open-mouth kissing of a positive carrier who has mouth sores or bleeding gums and any contact with their mucus membranes and an opening in your skin.
There are only 3 ways to prevent the transmission of AIDS. One of them is, of course, the proper use of a c0nd0m. Since this is not what you have in mind, it’s off the table.
The third way is to get your potential partner tested before each and every s.e.xual encounter. This is, of course, rather impractical.
So, the easiest way to avoid AIDS is to be abstinent. Not my pick, but to each his or her own. I’d much rather use a c0nd0m, which I did with each and every s.e.xual partner I had once I was smart enough to figure out that there’s some nasty stuff out there that I really don’t want to catch. Now that I’m married, however, my wife and I are in a monogamist relationship. Since we are both clean, we can enjoy s.e.x without a c0nd0m.