First woo the editor of your client publication.
Seriously though... going the media photo pass route is a double-edged sword. Unless you have a chum in the circuit media office or you know the series media rep (or other back door route), you will need to find a pass through an accredited publication. That means you'll have to please a photo editor rather than just yourself. Not so much in quality (although that is important) but in content. It makes for a very different race experience than just turning up when you like and shooting whatever you fancy (Mr Rick will probably back me up on this).
I crossed over from the 'beer' side of the fence to track-side about 20 years ago. I don't think I could go back now. I have to go to the races with a job to do, both for financial reasons (I'm self employed) and I think I might be continuously fretting about not being where I ought to be, or doing what I should be doing!
I've been on the "other side of the fence" some years ago but had other opportunities after a while (and got fed up with always the same races over here in Belgium). Would love to get back at the right side of the fence, but it just never seems to work out. In all honesty, I might think the quality of my pictures shouldn't be a problem. Being in front of the fence, feeling the pressure of getting the best images at the right place always pushed me to go further and get better stuff out of the camera. The more pressure, the better I could perform ... but it's hard to keep that motivation on the beer side of the fence.