Be prepared for stereotypes of Americans. Rich, fat, lazy and ignorant are, unfortunately, just a few that are thrown around. As a woman, you may also hear some overtly sexist, chauvinistic comments. Don't take offense or take it personally.
Expect to run into a language barrier. It is a toss-up whether the people you meet anywhere outside of Prague will speak English or another foreign language. It does happen that, even if they do, they will not admit it. Brush up as much as you can on your spoken Czech.
Get used to heavy food. If you're a vegetarian, get used to fried veggies and cheese dishes. Frying is an integral part of Czech cooking, as are thick sauces, pork and dumplings. The coffee is typically European, and therefore very strong, and if you drink water or soda, ice is hard to find.
You might constantly feel underdressed. Czech women are beautiful and invest a lot of time and money in their appearance. They may also dress more scantily than what you're used to. Accept it and get used to it.
Socializing and meeting new people is much more difficult for an American woman than it is for a man. Czechs in general are shy of meeting strangers, and Czech women are fairly distrustful of people they don't know. What's more, the pickup line does not exist in Czech culture. Be friendly but as conservative as you can be in a social setting, because you may otherwise be intimidating.
Remember that it will take time to make friends. Czechs are reserved and wary of strangers who are friendly to them. Once you get past that barrier, though, you've got a friend (even family) for life.
Understand that, because of the cost of living, it is normal and common for single Czech men to live at home until 30 or even older. Keep this in mind if you intend to date a Czech man.
Realize that the traditional male-female roles are still very strong in Czech culture: Women cook and clean; men do the repairs. It is never OK to be dating more than one person at the same time, and, most important, if you go on a second date you may be considered a girlfriend. It is accepted that men might expect their girlfriends to stay at home while they go out and meet friends.
Do not be shocked to see men or children peeing by the roadside. The most shocking things for American women in the Czech Republic are the hygiene or body odor, men or children peeing in the street, and that men might expect their partners to stay at home while they go out and meet friends.