I'm also a solo poly person who is not seeking a primary partner. I'm only 31, but I expect to still be happily unpartnered in mid-life.
Currently I have one lover (male; I'm a straight female), whom I met through OKCupid 10 months ago. It was sort of a fluke that I met him and clicked with him, as I was in a weird place emotionally and kind of mentally a mess at the time.
I was brand new to online dating, newly aware of my non-monogamous orientation, unsure how to articulate what I was seeking, struggling with anxiety & depression & insomnia issues, and struggling with a difficult graduate program. I was also grieving the bizarre and traumatic ending of an important relationship/friendship (which also affected my career very negatively) and dealing with a lot guilt/hurt/confusion over how/why the relationship had ended. This tied directly to my own sexuality and my feelings about non-monogamy & being solo, and meanwhile, I felt totally alone in a world of couples & monogamy. Plus, related to all that, I hadn't had sex since over two years previously. (I had largely forgotten that I liked it!!) So I felt, very, very confused.
In short, I have no idea how to advise you on solo poly dating, because I have no idea how I ended up in a healthy, happy, super-sexy situation that works for me! But somehow, I did. And now that I'm in it, I can articulate much better what I want and what I'm looking for. I feel a huge sense of peace, and I am now very confident in my dating life.
My lover is actively dating other people. In theory, I'm looking for other people as well, but in practical terms, I won't have the time or energy to date again until my thesis is turned in (three months from now!) and my grad work is over. Which will be awesome!
When that happens, I'll be back on OKCupid. I just don't cross paths with any single men these days. Despite having many interests & activities, I just don't.
Via online profiles, I will be doing some trial-and-error to figure out what works best to describe myself and what I'm looking for. Like NYCindie, I've found that the term "non-exclusivity" resonates with more men than "polyamory." Also like her, I am seeking mostly "casual relationships" or friendships with a sexual component.
I am no longer going to use the term "friends with benefits," which I had liked myself; but all men on OK Cupid think FWB means just casual sex (no actual friendship). So I learned something from my experiences with OKC last year.
I am comfortable with the idea of dating someone who has a primary partner, but my ideal is a man who, like me, loves being single and wants to have several "lover-friends" for fun & affection. We'll see what happens when I start actively dating again.
In the meanwhile, the issue I have been encountering is that it's really hard to convince friends & family that 1) I really do want to stay single because that's who I am and what makes me happy, 2) my lover is awesome but he's really not my "boyfriend" and I don't call myself his "girlfriend," 3) yes, I'm really okay (more than okay!) with him dating other people, and 4) yes, I really am non-monogamous myself, and I intend to stay that way for life.
The only other dating advice I can give is that I had to move my OKCupid profile from the tiny college-town-ish city I live to the big, awesome city an hour away. That's how I met my current lover, and that's where I expect to meet future lovers. The bigger city has a pretty large community of ethical non-monogamous folks (overlapping with the also large poly community).
Oh, I guess I should also say, as a solo poly female, I have felt more connection to the "ethical non-monogamy" crowd than to the folks who identify as "poly." (The poly people are nice & supportive & interesting, but they just don't seem to get where I'm coming from and don't seem compatible to date me). Maybe my brand of ethical non-monogamy isn't quite poly. That's fine.