Once the final results of all the exams are in hand, a student would then begin to narrow the list of university choices. Pick 2 or 3 that you think you may not get admitted into, pick 3 or 4 that you think you should be able to get admitted, and then pick 1 or 2 that you think are guaranteed admission. This gives enough coverage over various choices. If you are lucky, you might hit one in the university that you did not get expect to get admitted. These decisions should be made via consultation with faculty or knowledgeable people. Of course, many factors influence these decisions (program, location, tuition etc)
Once you have the I-20s, the decision now is to pick the one that suits you best. This is even more difficult, particularly, if you have more than one choice. One way to decide would be to make a list. Write down the pros and cons for each university (along with family members and/or friends) on a sheet of paper. Now compare the tradeoffs between them. This gives you a much better picture of what you should choose. Please make sure to involve friends/family during this process. Good Luck.