Work in the trade for which you desire to be licensed. All states require a period of verifiable work experience in the trade as a prerequisite to taking the contractor's test. This experience might be either as a worker engaged in the trade or as a supervisor.
Determine the requirements for a general contractor's license in your state. The website for the National Association of State Contractors Licensing Agencies provides links to the relevant agencies by state.
Don't try to go solo. Find a school to prepare you for the general contractor's examination and the swimming pool contractor's trade certification. In many states, a directory of approved contractor's license schools is available from the bureau of private postsecondary and vocational education. The U.S. Education Department page has links to vocational or continuing education departments by state. California's Bureau for Private Post-secondary and Vocational Education, for example, provides information for more than 50 contractor's exam schools statewide.
Know your stuff. In Florida, where swimming pool contractors abound, examples of topics in the state's swimming pool trade certification test include plan reading and estimating, excavating, concrete and shotcrete, finishes, equipment and operation and safety