Many students ask themselves this question and it seems that these days there is almost pressure to do it.

The short answer is, it depends. You should ONLY apply for Early Decision if you are 100% sure that this is the school you really want to attend. Apply ED only to your dream school, the one that you would be happy to choose even if you were admitted to all other schools.

Depending on the university, ED might give you a slightly better chance to be admitted. That is because, excluding the top 10 schools, you might find yourself competing with a weaker pool of applicants.

That said, ED is binding and if you get admitted you are not allowed to apply to any other schools or accent any other offers. Furthermore, you have to accept regardless of how happy you are with the Financial Aid you have been offered (although of course you can try and further negotiate with the school after admittance). 

Many of my students have been accepted to one of their dream schools via Regular Decision so don’t think that ED is your only chance to get in.

That said, if you have dreamt of getting into a certain school for a long time, then go for it.

The short answer is: Early Decision is binding while Early action is (generally) not. You may apply to only ONE school Early Decision, and to more than one school Early Action.

That said, you have to check carefully each university’s policy regarding Early action. Some, such as Stanford, have restrictive Early Action. This means that they do not allow you to apply to other schools as EA or ED, but you may apply to other schools Regular Decision. More on Stanford policies here.

It is standard practice to apply to two schools Early Action as that may give you a slightly better chance of being admitted, although that again varies on the university and is hard to measure.

Khan Academy. 

it is highly advisable that you set up a profile and use their SAT preparation materials for both the Math and the Verbal sections. In addition, Khan Academy tracks your progress and you can create an individualised plan of study.

The best topic for your personal essay is individual to you. There is no One Size Fits All formula. Express your individual personality in the most authentic and meaningful way to you. For more tips and detailed explanation, please watch the video and read the information here.

It is not compulsory to declare a major; however, it makes you seem a much more focused and passionate candidate if you clearly state an area of study. You can always change your major later. 

If you apply to an Engineering school, for instance, it is highly advisable that you show very specific interests because your application will likely be ready by Engineering faculty members who are much more interested in your Supplemental Essays about your particular projects and passions within the realm of Engineering than they are in your (usually) non-academic Personal Statement.