Once you make up your mind send `thank you' notes to all the professors you contacted. Specially those whose offers you are rejecting. This allows you to keep good relations with these persons and you may be able to collaborate with them on a research project between the two universities or when you meet them in a conference or symposium. Not thanking the people who helped you gives a bad reputation to egyptian students in general and affects others that may follow you. Think that another guy may abuse your professor and how can this affect your situation: don't hurt the others.
The next steps you depends greatly on the university you chose. You will
need to register and be at the university by late august if it is using
semesters. If your university is based on the quarters system your arrival may
be delayed till mid september. Any way, begin asking about the housing
options early so that you can get good prices and locations. If you have
children going to a nursery or school plan accordingly. Prepare your past
vaccination and medical records. Ask about car prices, driving licences,
medical insurance, ....
A friend fom inside the university can help you greatly in these aspects.