The decision, to become an exchange student took me some time and will of course take you some time. It is really important to think about some things before joining an organization that helps you to become an exchange student. I give you here some questions to aks yourself, and afterwards I give you my advice and my decisions to each of the points.
First of all, you should ask your self some of the following questions:
I wanted to become an exchange student, because I wanted to learn the American "Way of life", I wanted also to improve my English, and I wanted to make friends for lifetime and have experiences how other families live. My parents welcomed my decision, my mother even gave me the idea to do it, because she lived earlier for three years in South Africa. My parents thought it would be a cool experience for me, and I also could widen my horizon.
You should be able to change if you are an exchange student. That is one part of becoming an exchange student. I made the adjustment to change. You always should be able to change your old habits in a new family. Very important for that are realistic expectations, sense of humor, ability to communicate, be open-minded, to have the ability to succeed, and flexibility.
I was in the USA, speaking English was for me no problem, because I took four years of it in school. But if you would like to go to Japan or somewhere else, you should think about if you know at least the main vocabulary for a conversation.
One year away from home was not the world for me. And it never became a problem during I was in Utah. The time flew by for me. But for other people, they are really homesick, and I heard about some people that were really homesick.
I could keep my self busy, I worked on this homepage for example, but my host family was home very often took care very good of me, and they helped me to have a positive experience. But it could have came differently. What if both of your host parents work, there are just people in your family which are too young to drive you around and you live on a farm. What would you do? You need to find in those situations something that keeps you busy.
Another big question is, if you can solve problems on your own. There won't be your Mom who could solve a problem with your host family. You need to be able to solve problems on your own and find a solution. You also should be tolerant, and should accept everything how it will come to you. Just try to do your best in every situation and try to be tolerant. I helps no one, if you go to America, but you hate Americans. I had no problems with that, but some people do. And another thing is, if you are just becoming an exchange student, because you have a lot of trouble with your family, then don't go before all problems are resolved. If you leave in trouble, you won't help anyone.
I first couldn't believe where my organization sent me: to Utah, in a Mormon family. I thought they probably try to convert me on the first day. One girl in my class in Germany even asked me: "You are going to Mormons? Are you crazy?" She probably didn't realize what a great opportunity was in that fact for me. Actually to get a Mormon family is probably the best thing that can happen to you when you go to Utah. Utah is wonderful, and the people are, because of their religion much more friendly and try to help you. I had no problem with going to church every Sunday also. I am not member of any religion, but going to church was a different experience, because I had the opportunity to meet great people there. So if you have a problem going to a family of another religion, then forget going to the USA. On every coin or money bill is printed: "In God we trust". In the USA are people living from all kind of religions. It will be a good experience for you to go to a family with another religion. At least it was a good experience for me. Also be diplomatic enough to keep your beliefs on your own, if nobody shares them. Everybody in my neighborhood had a flag of the United States in their front yard. First of all I thought that is pretty crazy, but later I understood that the national spirit is much bigger in the USA. Better wait before you say things you didn't think about. It saves you a lot of trouble. Try to understand why people are doing different stuff in different cultures.
You need to keep your program rules and your family rules. I almost never broke any rules, and if I did, nobody ever found out. You still should obey all rules of your organization and your host family. It is also very important to keep the laws of your country, because first of all, you represent your country, and if you don't obey the rules, your organization will send you back home. For example I knew a girl in New York, she smoked, drunk, and took drugs against the rules of her organization. She also didn't obey the rules and curfews of her host mother at all. That is maybe not a very smart thing to do, because you still represent your country.
Try to figure out which organization most satisfies your needs. That means, you should read through a lot of stuff from different organizations and choose the organization that helps you the most. My organization was the organization which could help me the most, therefore I chose them. But it is also important that your organization prepares you for living in a foreign country. It is also very important that you have the right to drop out of the program without any problems. A student at my highschool had problems and was homesick, so she returned home after three months. That was her right, and she had no problems to drop out. Where you should always know your rights, you should also know your responsibilities, too. And it isalso very important to see if the organization takes care of your medical insurance.
I hope you can make the right decision for you and the people that are around you. Good luck!