The best way to know if a swinger couple is reputable and trustworthy is to research them online. Read reviews from other swingers who have interacted with the couple, see what their reputation is like in the local swinger community, and look at any profiles or websites they may have created. You can also get to know them in person by attending local events or talking to them directly. It's important to make sure you feel comfortable with the couple before engaging in any activities with them.