Applying to college is a complex process and is not something that can be done overnight! After you have completed your college search, it is time to start the application process. One of the most important things to do is to go through all the different schools' applications and organize the applications according to deadline. Make a list of due dates for each application. You must send it well before the due date because if the application does not get to the college by the given due date you will miss your chance to apply. Remember that early decision deadlines are different than regular application due dates.
Luckily, most schools have an online application process and most of the time you can make incremental changes before submitting the application. It is best to read through the requirements and prepare ahead of time. For example, prepare your essay in a format that can be uploaded.
If you apply using a paper application, make sure it is neat - no white out! If you can, type the application or print it.
You might also consider filling out the Common Application for Undergraduate College Admission. Over 150 colleges parcipate in this program, which allows you to fill out one application and submit it to multiple schools. Just make sure the schools you are interested in accept the common application otherwise you will have to fill out a separate application.