As a traveller you are allowed to enter new countries for limited periods only, the normal period being 90 days although sometimes it can be more (180 days in Panama, for example) or less (a friend of mine was only granted a 10-day visit when he entered Costa Rica from Panama), depending on widely varying conditions. It is for this reason that many times when you’re having fun in a country or you plan an extended stay, you have to do regular visa runs to renew your allowed stay unless you want to become an illegal inmigrant. This can be taken as a hassle if you want to take it badly, or as an opportunity to do some travelling, shopping, or whatever you feel you want to do on the trip to make it worthwhile. Depending on the actual border you are crossing you may have more or less problems associated with leaving and coming back. Normally all of this is regulated and you must remain outside the country for at least 72 hours before you are allowed back in, but this is usually just a mere formality and in most land borders you can just leave for an hour or so and come back in without further problems (I’ve managed to just walk around a building and go straight back into a country I was leaving…).
One thing that poses problems to many travellers is the need for an onward ticket from the country you’re entering. This is another mere formality, but it’s just for proof of your intention of leaving the country you’re entering and not just loitering in the streets for ever and ever. Many people will tell you that you need a return ticket, but this is only one of the options available to you. What they really want to see is an outbound ticket to prove that you don’t intend to stay in the country, and maybe also lots of money in your bank account or pocket.
Anyway, a ticket out of the country might also pose a problem to serious travellers of the kind that don’t even know where they’re sleeping tonight, and for whom planning an outbound trip in advance is not only unthinkable, but even distasteful. This is where, fortunately enough, there are some websites and/or other options we can turn to in order to get around this silly red tape. So, as proof of travel we can sometimes just show a booking, which means that if we book from the right site we can show a booking for a ticket that we haven’t yet paid, which is just what we need! 🙂
So, try to find a site that lets you book your ticket without having to pay for it and lets you print a pdf with your booking details that you can present as proof of onward travel at the border. Some sites require you to give passport and card details to actually pay for your ticket after booking, so you can just forget about it and your booking will be cancelled automatically. Neat!