Throwing a hat on backwards and running around with big equipment is not going to get you into highly credentialed events. Small-time events it could work. But, try and get on the field at an NCAA or professional sporting event or a highly popular concert and you will be turned away at the door. Not to say it's not worth trying, but I wouldn't count on it.
Getting a press pass from your local press association is not really that hard, even as a freelancer. All you have to is get 1-3 (depending on the press association) of their member publications to sign you on as a freelancer and they can apply for the credential. Getting signed on as a freelancer with smaller publications can be easier than some think. Just put together a portfolio and present it to editors. Some will turn you down, depending on your portfolio, but others will offer you an assignment to see how things go.
But, a word of caution, even a press pass from a state press association is only a first step. Most big events and entertainment venues have their own credentialing system where a state press association pass is only the first step to obtaining credentials.
ATV guy has another approach. If you specialize what you shoot and limit it to one type of event, it's fairly easy to freelance that kind of coverage out to specialty pubs and niche sources. I have friend who only shoots horse shows. He never gets into sporting events or music concerts but he has front row access to any horse show he wants. I have another friend who quit newspaper photography to shoot rodeos all the time. Often times, specialization is the key to starting a freelance career.