I am traveling overseas, and was wondering what the airport regulations and/or routine will be like?

I am in the United States presently and will soon be traveling to South Africa, and, later, London, England. I'm mildly worried as to whether or not the airport routine and/or rules will be different. If so, information would be extremely welcome, and if anyone also has any tips....Any feedback will be highly appreciated!!! :) Copious thanks to anyone able to help.