Nice post pragueface, but even people who can speak a little bit of Czech ca't find their way around seznam. I first tried it two years ago when an American friend's czech girlfriend and a different american friend both told me to try it two years ago. I had to get on the phone with the czech girl and have her spoon feed it to me, then half the answers you get are in czech only anyway.
A lot of how successful you are is going to depend on you. The guy who can pass as a rugby player can pull anywhere. And some guys can't pull anywhere...this forum is about where anybody can pull if they can back it up with a few euros...so this thread is a bit off topic.
Having said that, if you try seznam and you have a dictionary your czech can improve quickly and it can be fun! I will agree with pragueface and wan's results. Everytime I post i get about ten emails and 1 or 2 will be 8s or 9s, 1 or 2 look like i wouldn't be interested , and the rest are 6-7 s by my scale. So i will meet one or two that are in the 7+ looks category and i think I usually get 25% the first date and 50% of the others in bed by the third date. Every kind of girl is there. I met a fashion model, a lawyer, a webcam girl, 2 strippers, a hooker (for free, there are lots there that try to get money -- don't go for the buy me phone credit and i will call you scam), a shop assistant and a student! One girl who was a seven and thought she was a 10 offered to be my lover if i paid her school tuition.
You don't have to wine and dine them. just meet them for a coffee and if you like them invite them again later or extend your date.
But like any internet dating, probably half of them are a bit strange. I met one really pretty, 1m80 girl who was totally into s&m and she talked about it so much i just didn't feel like trying to get her home or calling her again. Anotehr was strange in a good way. She was from a small city one hour from prague and after the first night we were sort of friends and she would call me sometimes to tell me about her new affairs, then after three months she started bringing me her friends who wanted to try an American! None of them were as hot as her but I apprecieted the thought! Another one was from brno and she had me come meet her and her friends in a brno disco and when she thought i wasn't paying enough attention she jumped up on the podium, tore off her top and danced topless (she is the one who turned out to be a hooker).
The upside is that since the average is much better here in Czech Republic, you don't have to worry so much about ending up with a girl you would never want to go out with.
I would say that for people visiting Prague, if you can navigate the czech personals sites (or even try an english language site) the best use is to set up meetings with czech girls in smaller cities like Plsen or Brno, then go meet them. A lot of the really beautiful girls in those small cities are tired of the local guys who just want to get them in bed then have nothing special to offer, so they are open to new ideas!