Don't commit to more time than you can handle. You should also expect to discuss your medical history and anything that currently ails you. Some medical problems may prevent you from performing certain activities. You'll likely be asked to fill out a PAR-Q, a physical activity readiness questionnaire. Depending on your answers, you may be required to take another questionnaire to your physician.
Many doctors charge a fee to complete the form.
Once the trainer has all the information he or she needs, the two of you can begin to map out some goals - short and long term. Once that's done, the trainer will go to work to design a fitness program just for you. It's the trainer's job to teach you the program and ensure you can safely perform the exercises by yourself. The trainer-client relationship isn't meant to last forever. One last and very important thing.