to become a patent agent, all you need to do is take the exam. once you passed, you are an agent. but that does not mean you will get a job as a patent agent though.
you will need to contact law firms around you and look for opportunities. again, if you are in law school, things will be much easier. a big part of law school is to training you on legal writing, and to give you a general background knowledge of the law. both of which are very important for patent agents/attorneys.
then again, i guess it is possible to be just a patent agent, not a patent attorney. the thing is that i don't think a patent agent earns much though. last i heard, it's around $70k in my area. it could be higher in east coast, but i don't imagine it to be much higher. to bump the salary up, you really need to become a patent attorney, which means you have to go to law school and pass the bar exam.
it's not easy. so make sure you know what you are doing before you make the jump.
Good luck!