I think you're asking the wrong question. Submissives are as varied in what they're looking for as any individual ... curiously, because they are individuals. So what you should be trying to find out is what you're looking for, both as a type of relationship and in a partner. Until you're clear on that in your own head, you'll be disappointed.
For instance, when I was looking, I met an absolutely gorgeous girl who shared most of the D/s interests I did and was looking for the same level of relationship, but she was much more publicly open about her interests than I am. We were both clear about what we wanted and it saved a lot of time and heartache for both of us. Though it would have been nice to just once ... but I digress ...
Once you know what you want, you need to approach those who seem to be compatible. I can't tell you how to make that approach, because what interests or turns off a particular submissive is going to vary widely ... again, individuals.
Personally, I used one of the kink-friendly matching services to great success, but with a lot of effort. Off the top of my head, it probably took a hundred contacts to get to even ten email exchanges that showed even a hint of promise. Of those, most went nowhere, but a few wound up in meetings. Of those, even fewer wound up with both of us having enough interest to try a scene. Out of all of those, I wound up with only one wife ... more than enough, considering that I was "looking" for casual play partners at the time. It's not for everyone, but if you have the patience and can take being turned down a lot, it can work.
If you're very new to this, you might want to consider finding an experienced dominant who's willing to teach. That'll give you a chance to learn under controlled conditions. That could be important, depending on what your interests are. Someone once told me: If you want to use that on someone, you should know what it feels like yourself.