Your wording seems to presuppose that I don't know who else my partners are sleeping with. In the case of my primary partner, I do know, as we're very open about such matters. I also know he respects himself (and me) enough to be safe with other lovers.
That really is key: respect.
I can tell you from experience that respect and casual sex are not mutually exclusive, either.
Several years ago, I picked up a young man at a show, and we ended up back at his place. Before things got heated, he told me in a very forthright manner that, though he had never had an outbreak, he had tested positive and was a carrier of HSV-2 (most commonly referred to as genital herpes).
I ran through a mental check-list:
-No need to panic or ruin a fun night.
-Oral is out (for him).
-Oral is out (for me).
-Not going to risk intercourse even with a condom.
-Fisting it is!
We had a grand time.
Unfortunately he had a terrible habit of saying "I seen" instead of "I saw", which proved the grammatically incorrect death knell of our budding "relationship". But I digress...
"Casual" sex is never really casual. Every sexual act involving another person (or people) brings with it risks: from STDs, to pregnancy, to awkward "Hey...you. I explored every orifice of your body but can't remember your name" moments. Unless you're in a committed relationship and everyone involved is faithful and has been tested, you are taking a risk.
It is our responsibility as sexually active adults to educate ourselves, weigh those risks and learn to minimize them. Of course, there are the obvious precautions.
You mention condoms.
A friend once told me (many years after we had been lovers) that the sexiest, most memorable thing I'd ever said to him, was that I'd learned to like the taste of latex.
Nobody *likes* using condoms but with so many options---flavored, micro-thin, heat-transmitting, textured--- there's really no excuse not to use them. Faced with a choice between no sex at all, and sex with a condom...well, do you really want to be with the type of person who would choose the former?
Lube is something that might not typically be listed under safer sex options, but I think it's very important. Friction can quickly dry and tear a condom, rendering it useless. A little drop inside the condom and plenty on the outside of it will keeps things nice and slippery.
But do stay away from condoms with Nonoxynol-9 "lubricant". Certainly, it kills some viruses, but it can also irritate tender membranes and tissues, causing small tears and making you more susceptible to infections. (I won't even use harsh detergents to wash my undies--- I definitely don't want detergents inside me!)
But we know all this stuff--- we've read the pamphlets, heard the PSAs, seen the horrible pictures at the clinic. We know condoms aren't 100% effective against things like HPV and herpes.
It's enough to make you never want to touch another human ever again...until a minute later when the libido kicks in and you get frisky.
I'd be the last person to recommend limiting sexual activity to the confines of a committed relationship. What I do advocate is an exploration and redefinition of sex. I find too often people's definition of what "sex" is, to be rather narrow and confining in scope. Your average person will define sex as genital-genital contact, a smaller number will include oral-genital contact in that definition.
I would question their lack of creativity.
I often write about fairly "casual" Misadventures, but not all of those encounters fit within the above-described definition of sex. These lovers are sometimes strangers, sometimes casual acquaintances and I don't necessarily know their sexual history--- but very little will deter the Infamous CoatCheck Girl when she's on a mission! However, that's no time to be careless...
I haven't met a man yet who'll turn down a good masturbation show... or turn down a nice expanse of flesh upon which to shower the seeds of his effort (just be sure to negotiate face-shots ahead of time!).
And you avoid the possible pitfalls of the bar hook-up---whiskey-dick is nobody's friend!
Infamous CoatCheck Girl