internships after college or trade school or high school
mymemory's advice on getting an internship (as a primary job after school) is a great idea...but still start your own business, but do it small at first, get the info you need from working for a company, see what applies to you and your current clients, and then, break off and be 100 percent self employed
this applies for college, junior college, graduate school, trade school, and high school
after business college, i did a four month internship for the federal government and learned what not to do
and after computer repair school, with microsoft networking emphasis, i interned with a couple a large IT departments for a few months before taking on my own clients, and more important than what i learned what to do, i learned what not to do...school and hands on will tell you what's right and you will already know most of the stuff you need to learn, but by working somewhere else, you will see the priorities of what's important day to day and see a routine you can memorize in a short time
...so by doing even a one month internship, you can learn most importantly what not to do (steve wozniak worked briefly at hewlett packard and saw the blindspots of a large company and this helped him build apple with steve jobs)
...but beware, and don't get too comfortable in an internship and make it a long term job because you may lose the fire for being self employed and thus lose objectivity and become mediocre and be one of those long term employees who say, "i will start a business one day, really, i just don't have the experience or know how yet"...we have all seen those people and they are like those 75 year old smokers who say they will get around to quitting someday
a good internship is kind of like stealing ideas but almost every founding ceo learned first somewhere else whether it was woz at hp,
...or red-haried, kinky-afro hippie paul orfela hanging out at mcdonald's and using the ideas from the counter space, time motion studies, polyester blend uniforms, and franchise setups to build his multimillion dollar "kinko's" empire (so named after his afro)