I'll echo a few of the above, and add a few tips.
The national ID's are a waste of money. You have to get cleared anyway for most stuff by the agency that handles the event. You'd be suprised at what it takes to cover the President.
If you're the reporter for your station, you can do it. I'd suggest getting the perfed business card blanks at Office Depot, use your logo, title, add a photo, sign and date, get it laminated and wear it. Or get 'em professionally done.
Most spot news, just show up, identify yourself, and go where they'll let you.
Planned press events, talk to beforehand.
Most sporting events above high school, hand out one-shot passes. Some issue season or permanent ones. Call the Sports Information Director, PR person, marketing dept, or whoever handles it.
Artists: sometimes one on one by phone, through the label. Sometimes back stage at concerts, again through the label or promoter. Sometimes they'll hold press conferences. Sometimes you can record some at concerts, usually there's a limit on time. Again, call ahead and arrange.
NASCAR: call the track. Sometimes pressers, sometimes grab 'em when you can infield.
You need mic & recorder, cords that have xlr & 1/4 inch to whatever your deck's input is. Most folks have gone to minidisk. Cutting edge is flash recorders.
Attitude is important. If you act like you belong there, you'd be suprised where you can go. Be prepared if you get tossed. Also, bail money's handy.
Happy hunting.
;D