From what I have learned, at least regarding visas to the US, is that you need to show that you have enough money for your trip and stay and, more importantly, a reason to return: home, children, job, family, etc show this. They mainly want to know that you are not trying to immigrate and that you will not become dependent on the state. Obviously previous travel, even to other countries, helps quite a lot as it sets precedents for proper activity regarding visas.