First off, it's not entirely like scuba, in that with scuba; you get your lessons, and then your on your own. With martial arts, you're with the instructors for the whole thing [basically]. With that said, you can figure out as you move along if the instructor is the right one for you.
Many different instructors have many different styles and philosophies. For example, one instructor I had was very into the history and philosophy, so we did a lot with the history of the art, the meaning of different types of weapons, etc... That instructor was also exceedingly strict. Knuckle pushups were handed out daily for minor offenses. Major offenses were delt with in other ways [for example; there was an 'almost black belt' who was sparring with the head instructor. She demonstrated a lack of control with her strikes [no contact sparring]. He warned her 3 times to pay attention to control. The 4th time wasn't a warning, he sent her across the room with a kick...
Another school I trained at was much more lax in discipline, but had benefits in other areas.
It all depends on what sort of thing you want. But remember, any martial arts training takes a while if you decide to set goals like 'black belt'. You're talking a 2 or 3 year commitment at least if you want to go that route.
Definately go to a few classes and observe. Ask what the average time to reach black belt is [it's a loaded question and should actually be answered with questions and not something like "2 years; but 1 1/2 if you spend XXX". Beware of places that have different colored uniforms for different belt rankings; There is no pure style that requires that; it's a money making ploy. This doesn't mean it's a bad thing; for example one school I trained at had implemented such a thing, because without it he was going to go out of business.
Watch the classes, and watch the ranks. Do the green belts look good, or are they sloppy. Are the blue belts impressive. Do the brown [or red] belts blow your mind? If the blue belts are stumbling around and can't do multiple combinations in sparring... then they got there too fast; in which case the school is more interested in taking your money than training you. Ask how long between belt tests, and ask what sort of requirements exist for belt tests. You will find some schools that will test you for a belt every 3 months. You'll also find schools that will test you for a belt every month... but only if your ready. It could be 5 or 6 months before you're recommended for a belt test.
Both schools I trained at had scheduled tests every 3 months, most people would be qualified for the next belt after 3 months, but occasionally someone would be asked to pass over for the next three months. 10 levels = 30 months = 2.5 years to black belt [minimum].
Another question to ask is about junior [under 16] blackbelts. Is it an official blackbelt, or is it a junior blackbelt. Both schools I trained at had junior level belts. They held their belts and grades until they turned 16, where they had to re-test for all their degrees with adult standards. I've also seen schools that don't allow students to get a blackbelt until they turn 16.
But remember... after 3 months at one place, you can always [if you decide to continue] go somewhere else if you don't feel it's the right _fit_ for you.
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Next comes styles. The first question is 'hard or soft'. Hard styles [Tae Kwon Do, Shotokan, Karate] are more violent in nature. They are something you do in the school for exercise and the art. They serve near to no real world applications. Soft styles [Judo, Aikido] are more throws and holds. They actually can serve some real world applications, and therefore are used for 'self defense' as well. The basic jist of this is: If an attacker, comes at you, are you trained to get away, or are you trained to kill the guy. However some schools will mix soft styles into a hard style. One of the schools I trained at [I trained Tae Kwon Do] had an instructor who also had a blackbelt in Closed Circle Jujisu. So with every belt grade, we had different jujisu requirements as well. So while we were training a hard style, we still got some practical applications.
Many multi-style blackbelts received their first two blackbelts in one of each a soft and a hard style.
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Oh. One other point. Unlike scuba; where you choose the instructor not the agency; Martial arts you choose the style and the school. All blackbelts take a part in the instruction, and therefore you will be tought by many of them. What you care about is the requirements and the attitude of the school, not the individual instructors as much. There will be an owner/head, who will be the highest ranked in the school. What's his rank? There is [generally] 10 degrees of blackbelts. If your school is run by a second degree, and has only first degree blackbelts under their wing, that says a lot compared to a school with a 5th degree blackbelt, with multiple second and 3rd degree blackbelts active in the school. Some schools are small chains. So while one school I trained at had 3rd degree blackbelts running the place, they were still connected with the chain of schools, and all belt tests were done in Connecticut, under the watchful eye of the 8th degree blackbelt who's name was on the door! This association with such a high ranking Master also made it so the instructors in the individual schools weren't 'done' with their training, they were training for their higher degrees as well...
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So now that you have _way_ to much information... throw that all in the back of your mind and start with:
1) What is available in my area?
2) Do I want to do a hard style, or a soft style?
And if you don't know #2 right off the bat, start watching classes and see what you like.
[BTW: Steven Segal - Aikido (soft). Jeff Speakman - Kempo (hard); Jean Claud Van Damme - Karate? (hard).]
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