I chose to apply early decision to the University of Pennsylvania. I chose to do so because I was applying for a highly specialized dual degree programme that encouraged ED if it was your first choice (which it was for me). I visited Penn's campus twice and researched extensively while making this decision because if I were admitted, I knew that I would be locked in and didn't want to regret my decision (spoiler alert: I did get in and I don't regret it). Here are a few things I wish that I knew before applying early decision and what might help you make up your mind:
1. Only do it if the school is your absolute #1. If you have lukewarm feelings about it and are just applying ED to try and increase your chances of getting in, don't do it. You don't want to be stuck with a decision that shapes the next 4 (and potentially more) years of your life
2. Your application needs to be ready over a month in advance. For most colleges, their ED deadline is the 1st of November. This means that your common application, supplemental essays and testing NEEDS to be complete by this deadline. Also, you won't get the opportunity of using any other except your half early exams for your predicted grades. If you haven't had a great academic record in class 11, considering applying RD so that you get more of an opportunity to improve your grades
3. Buyer's Remorse is natural. There are always going to be colleges that you wonder about. It's totally normal. However if you don't think you would be happy at your ED school don't do it (I can't stress this enough)
4. Know that breaking an ED agreement for other than financial reasons has serious implications. You might not get accepted to any other schools in the United States as your HS may refuse to send out your application to these other schools. Also, if you break an ED agreement, that has potential consequences on future students from your HS applying to that university
5. Do thorough research about the university that you're planning to apply to. If you have the opportunity to visit, definitely do that because sometimes you don't get a sense of a place unless you see it yourself. Otherwise, watch videos, talk to current students, ask questions on this forum etc
6. Trust your gut. You have until decisions come out to change your mind.