One way would be to limit who can receive a passport or visa to travel to another country and another would be at the entrance to the country they may not be admitted for example due to inadequate funds to live. In my case, when I travelled by bus from Costa Rica to Panama, the Panamanian authorities required that I either have a ticket out of the country or a return ticket back to San Jose, Costa Rica.
You can read the guide words that are at the top of each page.
They help you by telling you what words are on that page using the letters of the word in alphabetical order.
Hope this helps