Here is a good list of ten qualities of an entrepreneur. The list has relevance if you are contemplating striking out on your own (or starting a new firm with partners). Item #4 is probably the hardest one to translate to the law (Do you have a unique service or product?) It’s hard to come up with a new practice area that the marketplace needs.
“Unique” in this context may relate more to the clientele you serve or how you deliver your services. For example: find effective ways to bill clients that do not rely on traditional hourly billing; identify an emerging industry that has a common set of legal problems; create a firm that provides a multi-disciplinary approach to solving a set of business or individual problems (making sure to adhere to the ethical rules which bar non-lawyers from owning law firms).
The point is that you need to distinguish yourself from service providers that already exist.