Job interviews :-o Just kidding but it worked for me.
Honestly, I think it's best to develop a good sense of what you like to do with your life, and then do it, but be aware of your surroundings and the people in them. Be open to conversation, and talk about your hobbies and interests and past adventures. The principle of attraction applies...you will attract what you project.
I went on Match and that's how I met my kids' dad, that relationship didn't work as a love match, but lately it's been working out well as a co-parenting match. He has a decent job and time to spend with the kids, he's not the greatest father, and he makes a lot of mistakes with their physical care which has been troubling, but the kids are older now and able to advocate for themselves, and if they get stuck in that respect, I go to bat for them.
I also met my last guy on Match. He started out well but disintegrated. It could have gone either way in a relationship, I was open to that. He crashed/burned after four months. I went back on Match and met a local guy, we get along okay but will never be more than friends.
eHarmony I have used a couple times. The first time was years ago and I met a guy who seemed to think because we got matched, that it was a done deal. He was infatuated with my intelligence. I didn't go out with him again after the first date. During the summer I had a subscription and finally met up with one of my matches, we went for dinner and a movie, but there was no click. It was a pleasant evening out nonetheless.
I got set up by someone recently and it was a fail. She really didn't understand me or my lifestyle. The guy she set me up with just wasn't my type at all. I have a very ecclectic, sort of dirt-bag lifestyle but serious work and academic undertakings. I'm not impressed with material things, nor do I necessarily enjoy the responsibilities and time that it takes to maintain them. I'm more apt to want to use my $ for adventures or self-development for me and my kids.
Then in the course of my day to day, I was introduced by email professionally to someone who had some work for me...I went out to talk about work, the interview turned into a coffee/walking date, and then that turned into dinner at a later date...major compatability...you just never know. I think I might have had my last first date for a good long while.
I think the dating sites are good to keep your game up and to have some fun and to get out of the house, but I haven't had good success in long-term relationships with them.