Hi Carag!
Welcome to CC--I hope you enjoy your time here. I can understand your interest in online dating. If I'm ever going to meet someone, it will most likely be online, although I am currently not on any dating sites. When you work all the time, go to a church in which the average member's age is 65, and don't have the time to do whatever it is that people do to meet other single people, online venues might seem like the only viable option.
I've been on all 3 of the sites you've mentioned and while it's been a long time, I would suggest Googling reviews of any site you're interested in. I don't like eharmony because they follow a strict formula--there is a questionnaire that will take about an hour to fill out, and they will only send you matches that supposedly fit within the restraints of that questionnaire. Unless things have changed, all matches are sent to you--you are not able to go through profiles or pick out the prospects you would like to talk to on your own.
As I said, I haven't been on these sites in a long time, so they might be different now. ChristianCafe had a rather small community and not many people, and Christian Mingle was known to count inactive profiles as part of their numbers (so that they could say, for example, that they have 5,000 members, but in reality, maybe only 2,000 were active and out of that, maybe only 20 members are active in your area, and of those, only 5 might be in your age range). I have also read stories about some sites paying people just to talk to members as if they were available members of the site in order to keep people's hopes (and membership dues) up.
I was thinking of rejoining Mingle a few years ago, but I saw that they eliminated their chat rooms, which caused me to lose interest. I found that seeing people interacting in real time cut down on some of the riff raff--maybe someone would try talking to you, but you would quickly find out that this person was also flirting with every other member of the opposite gender in the room.
My best advice would be to:
1. Stay realistic. I don't attract jocks, CEO's, lawyers and doctors, or guys who look like models in real life, and so if someone who claims to be any of those things online approaches me, I always stay guarded (I've only had 3 guys who would fit this description approach me online; 2 were catfish and the other, if he was real, was so arrogant that it was painful even to hear him talk, because it was all about himself.) As much as we would all like to think our online unicorn is out there and just waiting for us to login to the right site, I truly believe it's better to know yourself and what kinds of people talk to you in real life. My experience is that this doesn't change online, unless people are pretending to be someone they are not.
2. Stand your ground. Don't let anyone bully or manipulate you into giving out your information or doing anything you don't feel comfortable with. Some people might claim I'm a catfish but I don't feel comfortable with video calling, and I don't give out my information (phone number, personal email, etc.) unless someone has been willing to stick around and exchange messages for a while. Most people won't wait around that long, and many are just looking for a quick hook-up, whether claiming to be a Christian or not.
I could tell you a ton of stories, like the guy who said, "Well unlike some people (he was throwing shade at me), I'm an actual adult without being paranoid all the time" when I wouldn't give him my phone number after his first message. Or the guy who thought I would be a perfect mother to his son because of a similar family history, and when I told him (which I clearly state in my opening profile page) that I don't plan on having or raising any kids, he pretty much cussed me out, told me it was my loss, and then blocked me so I couldn't even make a reply. People won't like you if you don't agree to be what they want in order to make their own lives better.
3. Always put your safety first. I would recommend not meeting anyone in person until you've talked to them for quite some time, and when you meet, do so in the middle of the day (coffee or lunch is a good option), at a very public place, and park as close as you can to the establishment where you meet. (I have heard of some women being followed to their vehicles and assaulted, but this could happen with any kind of dating.) I would also suggest that if it's long-distance, request that the gentleman visit you first so that it's on your own territory and you have friends and family to look out for you, and if I met someone long-distance, I would offer to split the cost of his travel, hotel, and food, in order to make it fair.
I always let a friend or relative know I am meeting someone and text them before I leave and when I get home. For a first date, I always make it sound like I have somewhere to be ("I'd love to meet for lunch at 12:30, but I only have until 3 PM, because I'm helping my brother with a project," so that the other person clearly knows that someone expects to hear from me at a specific time, just in case they're planning on throwing me in a van and driving away.
Although there's a lot of ruckus you have to deal with, I can't say that I would trade my online experiences because I learned a lot and have met some very interesting people.
Even though CC isn't a dating site, I've also had some great online experiences as far as meeting people here and making new friends, both online and in real life.
Best wishes to you, and please keep us posted on how it goes!