How does a person go about getting a pat tent?

Is there a phone number or a address to send to, to get a pattent. I have heard there were places that do it for you but I hear they rip you off (is this true) Is there a simple way one can do it themselves to cut out the middle man or is it better to do it that way Has some one done this before and could you give me some insight, I know nothing about this