I farm Balthazar faction (goes pretty fast at Zaishen Elite) then trade for Z-keys and sell those. I'm sure there are better ways to make money, but this requires so little time and energy that I prefer it. Plus, I love trapping at Zaishen Elite... seeing the NPCs hit the rangers traps and insta-die is funny for some odd morbid reason.
There are lots of ways to make money in Guild Wars. However, without a working knowledge of the economy I would highly suggest looking at the farming section of the forums.
Find a build that fits your profession, go cap all the skills and try it out.
It is good to join a guild that may have some people that are familiar with a lot of farming builds and asking them for help.
Learning the builds at first may be tough, but just ask on the forums if you have questions.
If you have a monk, a good place to start learning farming builds is the 55 monk. It is a good place to start learning the intricacies of farming builds.
Of course, you can just keep doing quests and making money that way. Once you have money and a keen knowledge of the economy you can power trade. Of course, you can also run people, but that is becoming a dying way of making money unless you run people through dungeons in which case you still need a way to kill everything.
Asking about how to earn gold/money/items is not allowed. There are enough threads already, and there are forums more suited for those threads, like the farming forum.