I am going to assume that you are considering initial scuba certification, and you really don't know what it takes. If my assumption is wrong, my apologies.
In scuba, we talk about certification, and that means getting instruction from an instructor or instructors from a recognized agency. There are many recognized agencies. Some of them have independent instructors who work out of their homes. Many work for local dive shops.
In your area , there are scads of instructors representing many agencies and local dive shops. Asking this question in this forum will not be helpful because you can potentially get so many opinions that you will be no better off than you are now.
ScubaBoard has a number of sections, and one of them is for regional travel and dive clubs. If you scroll down, you will find the one for your area. I suggest you go there and use the search feature to get the names of some instructors and shops in your area. You can also ask a new question and get answers from knowledgeable people who read that forum but who don't generally read this one.
You should also go to some of the "stickies" at the top of this forum and get a sense of what some people think is good advice for new divers.