With your media pass you can walk in pretty much any normal entrance you want, just flash your badge. They'll probably do a quick search of your bag then you're good to go.
The picture above illustrates the route I take to get in. I enter the normal entrance on the Jervey/parking lot corner, walk allllll they way around to the far end of the stands, then walk down some green stairs (guarded by an EPI staff member, just show them your badge), and then enter a big unmarked green metal door in the dugout marked with the red arrow. Walk in the door and turn slightly right and you'll see a big open kitchen and sitting area - that's where you should leave your bag and laptop. Girls - you might have someone try to tell you that you can't go in there because someone thinks it's the baseball locker room or something like that. Good luck - I would argue that it's the only safe place to put our camera bags.
Where you can go
Now that you're in, let's go over the rules
There are a lot of rectangles in this picture, but I promise it really isn't too complicated.
Green - you can always be in the green areas. There's a little photographer area on the far side of the home dugout that they want us to camp out in. This is the far left rectangle in the picture above.
You can also shoot from pretty much any open seat in the bleachers that is orange or the normal-person green ones. This is a great way to get a variety of angles or mess around with some wide angle shots. This includes the outfield - take a lap around the entire stadium and take pictures wherever you feel like, even at the top of the outfield bleachers.
Yellow - Depending on who is setting the rules that night or which photographer is shooting it for the Athletic department, you may or may not be allowed to be there. This is where the bat+ball girls sit (you should talk to them, they're all super sweet and actually enjoy watching baseball)(Don't talk too much though or the bitchy TV lady will yell at you because the microphones in front of you are on) It's a great place to take pictures of the players batting or the pitcher.
Red - You can take pictures here for 1-5 minutes before they make you leave. They're technically reserved seats for rich people but usually 80% of them are open, so you can just plop yourself right in front of the net behind the pitcher and get some awesome shots. Due to some form of optical magic, the net will be invisible to your camera when you have any kind of zoom lens on it close to the net.
Press box - The press box will often have food at the beginning of the game. You should definitely go up there and check it out and grab a plate of food if you want. Also a great place to network if you're into that kind of thing and the people in the press box aren't too busy. Just don't go opening any doors in the hallway because the important people for TV/News/Radio stations are behind the closed doors.
Okay so there are two parts to a typical baseball game: Before sunset, and after sunset.
Before sunset the pictures will come out great!! It should be plenty bright, the lighting is usually at an angle thanks to games starting at 5pm or 6pm, and it's just all around a good time. For daylight I recommend
Shutter speed: 1/1000 or faster
Aperture: Depends on lens. f/2.8 is great
ISO: 400 ish
White balance: Auto or Sunny
After sunset the stadium lights come on and things get tricky. The lights might seem bright, but they really aren't. Your success after dark will really depend on your gear. Play around with the shutter speed and ISO (keep aperture as wide as possible or close to it). Typically your action shots will mostly be blurry at any shutter speed slower than 1/400s, but your pictures might be too grainy if you go faster than that (and higher ISO than 3200).
-Some sort of telephoto (200mm+) for action shots and close-ups
-A wide angle for stadium shots and team shots
•The faster the shutter speed the better
-1/4000s minimum if you want to freeze the ball
•Use fastest frames-per-second setting to have a better chance of catching the ball in-frame
•At night, find moments instead of action
-Smiles, celebrating, crowd shots
•Look for variety
-Get elevated, go down to ground level, wide angle shots
•Unless wide angle, crop tightly!