Rimming is risky for the person doing the rimming, since it may expose them to parasites and hepatitis A. You and your partners should wash the anal area thoroughly, before engaging in any oral contact near the anus. Douching is not a good idea, since it can damage the anal canal and drive infections further in. Sex toys can pass on parasites, hepatitis A, HIV and a number of other STDs. Cover sex toys with condoms, or wash them carefully with bleach and rinse well before and after using. Keep in mind that the lining of the anus is easily damaged by fists, dildos and other sex toys, so precautions should be taken.
Routine testing is very important for people who have casual sex.
You can pick up a number of STDs without having symptoms, so testing may be your only way of knowing whether or not you're infected. If you have casual sex, get a syphilis blood test at least once a year, depending on how many different partners you have had, and whether or not you had unprotected sex. You may also need urethral, anal and throat swabs for gonorrhea and chlamydia, depending on what sexual activities you engage in. Don't assume you're negative because you feel well, or because you haven't had unsafe sex for a long time. Also, don't assume that your sexual partners are HIV negative.