I think you need to make a distinction between Federal and State needed certification, and sailboat instruction. There is absolutely no Federal requirement to own a license or certification for recreational motorboat use. About 45 says, but have differing needs on the basis of the duration of the watercraft, variety of vessel, chronilogical age of owner, etc. There is out the academic needs by state at this from NASBLA site.
As far as competency is worried, there are several great methods for getting instruction. For classroom training, both the and the offer cheap classes in navigation, rules regarding the road, seamanship and so forth. However, i do believe you should think about on-the-water training, which can be mostly taught by for-profit sailing schools making use of either materials from or United states Sailing Association. Essentially, you would work yourself until where you had been bareboat or passagemaking skilled.
Then move out and sail with good sailors and study on them. Sail in challenging places with existing and wind. Sail on various ships, specifically small ships which are sensitive to improve your sense of touch.