Early Decision and Early Action are for students who have isolated one university as a top choice. These students have already done all the research they need to know that this ONE college is the one for them. These students will also know that they have a reasonably good chance of being accepted. By looking at college guides and reading on college's websites, you can find the average GPA and average SAT or ACT scores of students who were accepted in a previous year. You can compare your grades and scores to see if you have a very good chance of being accepted.
Early Decision usually means that you send your application to your top choice much sooner than the regular application cycle. The college will let you know whether or not you have been accepted much earlier in the process. Those students can move on to financial aid and scholarship applications. Colleges will expect that you will accept their offer of admission, but you do not have to sign a contract.
You need to follow all of the steps listed above, but you will turn everything in sooner. You will concentrate on only your top choice for Early Decision.
Early Action is very similar to Early Decision except that by applying Early Action, the student promises to accept admission and attend the college. Before you apply Early Action, students need to be absolutely sure that this is the college for them.
When you research colleges, you will see that some say "Rolling Admissions" instead of a deadline for admission.
If you decide late into the process to apply to a four year institution, a college with Rolling Admissions might be a good solution. Universities with Rolling Admission will accept students until they are full. If you decide too late, there may not be any space left.
If your top choice college has Rolling Admissions, you should set your own deadline near the other colleges deadlines. It is important to be as disciplined when applying to these colleges so that you will have a good chance of getting into your top choice!