The next question is: "did you have to send transcripts and reference letters individually to each school? It just seems a lot to ask for from referees."
Yes, I did have to send transcripts and letters of recommendation to each school. However, each school may have its own procedures and rules to do that.
First, I'll write about transcripts.
You will need to send transcripts from your undergraduate degree, and also for any graduate degrees you have after that. So, in my case I had to send transcrips from my bachelor's degree, my Executive MBA, and my Master of Science.
If your transcripts are not in English, you will need those transcripts issued in English by your schools or have trem translated. In my case, they are in Portuguese, so I had additional cost to translate all of them.
Most schools require that you send your transcripts online during application, and then you will be asked to provide official printed copies only after you accept an offer. But there exceptions, some schools ask for official printed copies during the application too. Schools usually describe those procedures if you look at their websites.
But there are surprises. I applied to a school which seemed to ask only for online transcripts during application. I did that, but after my application was sent, I received an e-mail informing I should also send official copies to its mail address. So, I had to hurry to provide copies I did not expect to need.
If you will send transcripts online, you will need to scan transcripts. Sounds simple, right? Well, I also had a few surprises during the process. Usually, it is one file for each degree you have. If your transcript has several pages, you should join them in a single file. Several types of files may be accepted, but pdf is a popular choice.
But several of them have a file size limit. You can't send a file of any size. The big problem here is that schools have very different size limits. Some of them allow big files. Some of them allow only ridiculously small files. Take my bachelor's degree transcript as an example. It is several pages long, and I had also to add several pages of translation. It was really hard to adjust the size of over 10 pages of scanned images to a very small size, without rendering the document illegible. So, I had to create files at very different resolutions for different schools. For those which allowed large files, I sent higher resolution scans to be easier to read. For those which allowed small files, I had to create the largest file I could within the limits each school established.
For those schools which require official printed copies, there will be additional bureaucratic procedures to follow. You may be asked to include an ID form in the envelope, for example.
Now, I'll write about Letters of Recommendations.
You will typically need 3 Letters of Recommendations. In rare cases you will only be required to send 2 letters, and in some cases schools allow you to send more than 3 letters if you wish. But 3 is the norm.
Ideally, those letters will come from known and experienced academic researchers who can write in a very positive way about your potential as a researcher. The farther you are from that ideal, the weaker is that letter for you application. If it is not from someone with research expertise, it willl be weaker. If it the evaluation is about other aspects that not research potential, it will be weaker. If it is not positive, it may kill your application.
You will provide schools with the e-mail addresses of your recommenders. Those e-mail addresses should be from institutional domains (email@example.com, for example), and not a generic e-mail (firstname.lastname@example.org, for example). After you do that, the school will send an e-mail to those recommenders, who will then have access to the school's system to post their letters of recommendation.
You will not be able to see those letters. You will be able to see the status of those letters. So, you know if a professor has sent a recommendation, or not. You can send a reminder, if a professor is taking too long to sent a letter, or if the deadline is getting dangerously close.
You will be asked if you want to waive the right to review those letters. In my opinion, you should always waive the right. If you do not waive, the person who is recommending you may perceive it in a negative way. Professors may think you don't trust they will write a good letter of recommendation. And, if you don't trust them, why should they help you? And, if you do now waive the right, you will only be able to review that letter after you have been accepted. So, reviewing that letter will not help your application at all, but may have a negative impact.
Is it a lot to ask from referees? Yes, it is.
If your referee is an experienced researcher, he/she will be probably used to the process of writing and sending letters to many schools. They know applicants usually need letters for more than 10 schools. If you ask a recommendation from your boss in a corporation, on the other hand, your recommendation will be weaker since it is not academic and I guess he/she might think you're asking too much.
But remember that your recommender is doing a great favor to you. A professor may also benefit if you get into a great PhD program, but you are the one to get the most from those letters.
So, ask people who have a good relationship with you. People who don't like you, or don't know you, will not want to recommend you. They will decline when you ask, or will write a bad letter.
Also, help them to write the recommendation. Talk to them, send documents which they can use to make a stronger letter (your research paper, for example).
Give them enough time to write and send their letters. They are probably busy people. If you ask them to stop everything they are doing right now and write ten letters because the deadline is tomorrow, the results will not be good.
If you need 3 recommenders, think of more than 3 people who can write those letters. If something happens with the letter of one of them, it is good to have a backup plan.
Keep them informed about the process. You should know the deadlines and which schools did not receive letters yet, not your recommender.
In my case, my letters of recommendation were from 3 professors I studied with during my Master's. One of them was my thesis advisor, a really great professor, who was very supportive during my thesis, always willing to help. He was glad to see that I applied to many schools, for example, since it showed him I really wanted to keep going in my research goals. Another is the co-ordinator of the business graduation program, who also helped a lot during my thesis, and he is very interested in my progress, since that shows my Master's was good for me, and so it can increase the reputation of the program he is responsible for. And the third letter was from a professor who is very experienced in reasearch, with great network, and who was very open to discuss my future in research, and helped me during my first academic event, where I presented my paper.