2 years ago, I did one in Toronto at the Skydome / Rogers Centre... Whatever they call it these days...
I emailed the team first, got permissions, made arrangements to show up early, not many people around then. Had access to parts of the field near 3rd.
We also got kickass seats, courtesy of the Jays (or more precisely, one of their PR guys) but we didn't stay in our seats long. We went to the 5th deck, most of it is off-limits at most games, and had great down-angles to the field. Went to various areas, it was a blast...
Flash was allowed, but only on-camera. Everywhere we went, someone escorted us and really helped move people and cut in some lines... Lots of cheering from the beer lines whenever I posed them and asked for a kiss or a 99% kiss...
24-70 and 50 1.4 and 135 was all I had brought, on a 5D2 and 40D