Figure out a taxi business rules and regulation where you live for becoming licensed, because people would not hail unlicensed taxicabs.
How to gain more customers ?In taxi business, you must find out where the taxicabs are limited and when people used to hail cabs. If you are living in a smaller town, then you must measure customer base and start market your taxi company to gain more customers. If you became familiar with demographics, then reach more customer by branding your taxi business. You could make business cards or a website for your potential customers to ease taxi booking. Create strong relationship with your repeated customers, it will bring your business into the next level.
Typically people used to hail taxicabs from hotels and airports, so be available in these particular locations and join the taxi queue if any special requirement. Hotel bar, one of the most common place where people will hire a taxi after they have been drinking. Make a deal with local bar owners and make them to call if any customer needs taxi service, feasibly you can provide offer to drunken people.
Usually senior citizens are no longer available to drive a car so they might often need a taxi ride to going out. Let yourself available for senior citizens in your area and build a relationship with them. Be creative and find yourself with steady stream of taxi business.