The answer to this question can be very personal. If you get into one type of engineering without little knowledge about what it invovles, you might end up hating it or loving it. Who knows? You can know by educating yourself now. There are lots of different ways to do this and there is probably not one that covers everything you should know before choosing which field to study.
Job shadowing is a good one. You might want to job shadow more than one civil engineer and the same goes for other fields you are interested in. Many jobs are different and two civil engineers will probably do some things that are completely different. Ask engineers their opinions of their jobs. Talk to professors and students of engineering.
The last one I suggest which should be of great help is to start working on projects of your own. Pick projects that relate to the fields that you might possibly want to study. There are tons of electronics projects to work on for electrical engineers. However, a civil engineer might also use electronics to help them assess the conditions of projects involving concrete and steel structures. A mining or metalurgical engineer might work on projects that involve rocks and geology as well as forging steel using a homemade furnace.
Here are some websites to help you get started on your own projects:
Instructables,
Make magazine and website,
Arduino,
Parallax,
Raspberry Pi,
Hackaday,
YouTube,
Linux including CAELinux, and
WISC-ONLINE for all the tutorials they have of many subjects.
Systems Engineering. It is the field related to high risk large projects. Most of these projects are the ones that really make a difference in this world. Launching a satellite into space, building a dam, developing a new product like a car or an invention.
Do not go after any engineering discipline if your aim is primarily to get fun. You can only handle engineering if you have interest, devotion, and serious enough to meet the tasks . To get a rewarding job you have to be good at it and prolific.
I am personally trying to get into engineering design but as the last comment said it is completely up to personal preference, depends what you enjoy doing :)
I was thinking maybe civil?
