There are quite a few requirements to being a flight attendant.  While only a high school degree or equivalent is required for flight attendant education, any college experience, even if you dropped out, is a major plus to your application. 

Studies show that over one half of flight attendents have at least one year of college education. 

Another important aspect of becoming a flight attendant is having good social skills and experience  However, many companies are willing to bypass your lack of social skills/ experience if you have at least some college experience.  Airlines believe people who have been to college are more mature than people who haven't, and learn good social skills while there.  However, if you have no college experience, or no customer service experience, your chances of getting the job fall drastically.

There are numerous minimum standards you must meet in order to become a flight attendant.  Some may seem unreasonable or odd to people, but since flight attendants are the only ones who have direct contact with the customers, these are necessary.  A pilot never sees the customers, but a flight attendant is constantly checking on people to make sure they are comfortable, bringing drinks or food to customers, or making announcments. 

For men, they are not allowed to have hair beyond a certain length,, and in some cases not even allowed to have facial hair.  In both sexes, you cannot have any visible piercings, excluding your ears, no odd hairstyles, no visible tatoos, and things of that sort. 

Speaking a second language is a plus on your application, and there is even a specific job where you make announcements in a different language, or if you are on an international flight, service those who speak the different language. So making language development a part of your flight attendant education can be very helpful. People with that type of job get paid more than people who only speak one language, but since not every flight needs someone who speaks a second language, it is not a requirement. 

If you don't know and speak english fluently, however, no United States airline will hire you.  There's no exception to that rule.

They do an extensive background check on all potential applicants to find out if they have a history of drugs or alcohol problems, ever had any run-ins with the law, or if you lied about your body measurements, such as height or weight.  Airlines prefer their attendents to be in good shape, and have a target height they aim for, however that is not strictly enforced.