First and foremost, see if you can get an internship in a local planning office. Even if it is only for a few weeks and you have to do it for free, you will gain valuable experience and get a good feel for what the profession is like. There is a high "burnout" factor among planners and you'll do yourself a huge favor by figuring out if you want to be a planner now rather than after 2 years of grad school, student loans, etc.
Qualities? Don't expect to make a fortune in this field. I think people who stick with planning as a career do so because they get some degree of personal satisfaction from making a difference in their community. Planning is NOT for everyone. No amount of training can prepare you for the amount of politics you'll have to deal with. There are a lot of variables in the planning process you can never control. Planners are always dealing with competing interests. There are times when you can do everything within your control 100% correct, but projects won't go your way due to political pressure, etc.
Planning can be an extremely frustrating field, but it can also be quite rewarding. I've only been at it a few years. Some days I like my job, some days I want to pick up and leave. Honestly, I think I'll stick with it because it tends to be intellectually stimulating and I just couldn't see myself selling real estate or something like that.
Absolutely, positively do an internship. Talk to experienced planners and listen to what they have to say. Ask yourself if you could see yourself doing the same thing for the next 30 years. It's a tough decision to make when you're 22 or 23 years old.
Having a hot temper is definitely a bad trait for a planner; you have to pick your battles and not take defeats personally. You can be ripped to shreds in public by your Board (when that's politically advantageous to them) and the next day they're extolling your virtues. And you need to be detail-oriented, as a seemingly simple project may end up in court one day, and you'll have to justify your reasoning. I think Brent hit the high points: you're doing a public service for your community (as opposed to being a shill for some half-baked development), and it can be fascinating work. And yes, go for that internship. You may find you're more suited for another field, but remember, there are many different types of planning (local, state, regional; long-range, short-range, historic preservation, trails, etc.)and you may find that one piques your interest more than another.
I was wondering the same thing. I rencently changed my major at the University of NH from political science to community development because of my interest in the area. I had some doubts until I took an assessment test at www.assessment.com. This site gives a lot of info about many different career areas. I'm sure it will be helpful.
The trick to getting accurate results is to go with your first impulse and really understand the question that is being asked during the test.
Good luck and go for it!