I have done lots of researches on the Internet but I’m not sure if I have found enough information or not, since most pages only give general views. I need detailed information on college admission process (GPA, SAT, IELTS, extracurricular activities, how many essays needed…) from someone experienced. Thank you and also sorry for my English.
Starting with this site, there are a number of articles of college admissions: https://www.collegeconfidential.com/topics/admissions
In general, you will not find a cookie cutter guide for the topics you listed, since all of top American colleges and universities practice “holistic admissions” and vary widely about what importance they place on ECs, essays and the like.
There in not one place to find all the answers you seek since, as noted above, each college has their own requirements and preferences. https://bigfuture.collegeboard.org is a good general place to start, as are the undergraduate admissions web pages for each college in which you are interested. Here is one example: https://www.wm.edu/admission/undergraduateadmission/how-to-apply/freshmanapplicants/application-checklist/index.php
Basics:
Common/Coalition App. Most schools take in applications through the Common App or the Coalition App. There are some that require their own app. The Common and Coalition App ask for basic background information which would include demographic info, school academic record, standardized test scores, extracurricular activities and a personal essay. The site is also the portal through which your guidance counselor and letter of recommendation writers submit their reports and letters. All of this information will be submitted to the colleges you apply that accept applications through these portals. Most schools will have a separate supplementary section in the Common or Coalition App that may ask more detailed question on your interests and background, and most have further short or longer essays to submit. I recommend going to the Common App site. It is free to set up an account and you can select schools you are interested in to see the application information you need to start gathering.
Standardized Tests. Most schools require either the SAT or ACT, although more schools are going test optional. If you are an international student from a non-english speaking background, the TOEFL may also be required. Many schools require or “strongly recommend” SAT 2’s. There is also a place to put down any AP Test scores, but that will not be a requirement.
School Reports. Your guidance counselor will be asked to submit a report on your high school record and transcript.
Letters of Recommendation. Many schools will ask for 2 letters of recommendation, preferably from teachers of core academic subjects that you have taken the past 2 years (junior and senior year). Some schools may either encourage or discourage (many more discourage than encourage) other letters, including letters from non-teachers.
Financial Aid. This will be a completely separate process. Your parents will need to put together information on income (usually verified through tax returns), assets and liabilities.
As each school has its own requirements, you need to first come up with your list of prospective schools. Go to each school’s admissions website to see what the requirements and deadlines are (may be different for internationals). There is also often profile data, e.g. GPA, test scores, demographics of the most recent freshmen. There is also often subjective indications of what they “look for”. Another source of school data is to Google “[School] Common Data Set” which will give you very detailed information about existing students and what the schools report as being important in their admissions decisions.
Colleges do vary on how their admission processes work, and what criteria they consider.
Common data sets or their reflections on collegedata.com can give you a general idea of what each college considers to be more or less or not important. Generalized averages can be found at http://talk.collegeconfidential.com/college-admissions/2131779-what-colleges-use-in-admissions-according-to-cds-listings.html .
It looks like you are an international student. Do a quick search for AMIDEAST and EducationUSA. That should get you links to a lot of information, and contact information for the advising center in your country.
Also, how much you are willing to/can pay is also likely to be very important.