If you want to succeed as a consultant, you need the right stuff, in terms of both skills and personality. Success means more than just having a successful business; it also means being happy with your job. Many people are not suited for consulting, which may explain the relatively low number of consultants compared to the number of people with "real" jobs.
To see if you are potentially one of the lucky ones, first look at your professional skills. You need a solid set of skills related to the field in which you are working. Do you have to be the world's greatest expert in the field? No, but you do need to know at least as much as your potential clients. You can actually develop a lot of your expertise through client work. The result: your clients will pay you to become an expert! This will happen quickly, because clients engage consultants not because they are too busy, but because they have difficult problems. For at least half of my consulting jobs, I had little idea how to get the job done, but I accepted anyway. And so I learned quickly, and slowly became a true expert rather than just a self-professed one. This process requires being very resourceful and creative in problem solving. Having a large network of contacts also helps, since the answers you'll need will often be in somebody else's head and rarely be in a textbook.
Your personal skills are as important as your technical skills. Clients ultimately are people working with other people. People are more likely to hire you if they like you. It helps if you are a positive, outgoing, cheerful, and likeable person. You must also be results oriented and be completely dependable, especially if you want repeat business. Each client must always feel that he or she is your most important client, and that you put his or her interests ahead of everything else.
As for work habits, consulting jobs are often long and complex, so you need to be able to pace yourself, schedule realistically, and be able to manage your own time. All these considerations are readily understandable. What is not as obvious is whether you will be happy consulting.
Realize that the goal of your first year should be to get your business started and to survive. Don't expect immediate riches. Have a cash reserve to be able to live without work for at least six months. This does not mean you won't be working for six months, but it will give you a psychological edge. Your chances of finding work when you're desperate will be as low as your chances of getting a date when you're desperate. Clients hire consultants that appear successful, because a successful consultant implies a competent consultant.
The quality you most need to stay happy as a consultant is the ability to live with uncertainty and a lack of structure. If you like working a regular workweek, you are in trouble. As a consultant, there will be periods when you'll work less than the traditional 40 hours a week, and periods when you'll work much more. At an early stage of my practice, when I didn't know how to schedule and manage projects, I once worked twelve hours a day, seven days a week, for a two-month period. There are also frequent periods when it won't be clear what your next job will be. Fortunately, this will happen less and less as your practice consolidates.
Keep in mind that you will rarely be thanked for a job well done. Your job is to make your client successful. The manager who hired you is the person that gets the glory; you are his or her tool.
And don't forget the time it takes, above and beyond the work you'll do for your clients, to run your business. Budget between half to three quarters of your total time for client projects, and set aside the rest of the time for doing things like maintaining your office, taking care of the accounting, and marketing yourself to generate future business. Some people, like myself, love this multidimensional aspect of consulting, but it's not for everybody.
Finally, you will always be an outsider in any organization where you work. You won't be privy to key internal decisions -- but you won't have to go to the annual company picnic either. If that's a relief, then you're off to a good start.