You have to make sure the instructor represents a certifying agency that's recognized world-wide and not just a resort course that's only good for that resort. I favor formal classroom and pool sessions ending with 2 days of open water check-out dives. Having classmates broadens knowledge including hearing answers to questions you yourself would not think of asking. Plus you get to see why certain diving faults (when exhibited by your classmates) are not acceptable and what's the proper way of correcting them as demonstrated by the instructor. Soon after being certified, I think doing dives in a "non-challenging" environment (example- at daytime, shallow depths, no currents, etc.) to hone in your skills and gain confidence and experience is a must. You then take advance or specialty courses to further develop your skills and guide you in your particular field of interest in diving. Be aware that your starting dive course is just that- a start.
