Meet up with a professional civil engineer and ask a few well thought-out questions as to what working as a civil engineer is really like. It's surprising how people will gladly give a little of their time to help out an aspiring fellow professional.
Get an internship and spend as much time with professional civil engineers as possible. It's only by exposure to the industry that you'll be able to get an idea of what it's like to work in it.
Figure out ahead of time what type of civil engineering path you'd be interested in, and consider the future of that industry.
If you choose a mature field of civil engineering, you will most likely have a slower but stable growth in your career. If you choose a niche field, you'll probably make more money, but sacrifice the experience in becoming a well-rounded civil engineer.