My best advice is to think BIG! When you start your business you're tempted to see the entire scope of the project, break it down into manageable little forkfuls, and then eat the elephant one bite at a time. This is an excellent strategy AS LONG AS you're keeping your dreams and future goals in mind. Is your dream to one day sell your business and retire in luxury?
Begin with the End in Mind
Then you need to make sure to put into place a system that will allow you to phase yourself out once the business is up and running. Is your dream to create a multi-million dollar corporation and release an IPO? Then make sure you're counseling with somebody who has done that before. In other words, always BEGIN with the END in mind.
Second, though no less important (and pertaining much to my own chosen field) - remember, if you're able or willing to do something that other people can't or won't, there's money to be made. Be creative! Find activities that you enjoy (or at least don't mind) doing, and then see if there are any ways that you can hire yourself out.
Word of Mouth
Finally, word of mouth advertising is CRITICAL for startup service endeavors. Bend over backwards for your customers and they might mention your company to their friends. Just do the service you offer, and they're just going to pay you for it. Amaze your customers with the service you provide (for a good book on how to do this, check out Duct Tape Marketing by John Jantsch)