1. I don't know if they still have it there, but Ralph's grocery store right near the con was a decent value if you want to cook your own stuff, make sandwiches, etc. The deli area can get quite busy now though.
2. Bring your own pens, Sharpies, pencils, etc. If you want somebody to sign something, doodle in your sketchbook, etc. Not everybody has one.
3. Hand sanitizer. I don't know if they have it there now, as I haven't been to SD in a few years, but there are definitely some folks who don't wash after visiting the restroom.
4. If you want autographs or photos from the 'superstars' who sign in the upstairs halls, you'll likely have to skip their presentations. i.e the big film presentations. The lines are already way too long at the autograph areas from people who didn't go to the presenations. Even if you want to see the presentations, you have to line up a heckuva lot earlier now than a few years back.
5. Bring some kind of folders or hard carboard if you're carrying small prints in your shoulder bag or backpack. It'll give a bit more protection when your bag gets bumped by Gandalf's staff or Pikachu's tail.
6. Bud Plant, Check their booth always. At least I do when I go. You always find deals on books and other stuff that you will pay much more for at other places. Also, if you miss picking up an autographed sketchbook or two, Bud Plant usually has a few towards the later days of the convention.
7. Often, your cell phone might not work. Whether it's the rumored cell phone blockers, or the thickness of the building or the sheer number of signals in the area. Step outside the con if you want to make a call with it.
8. I cannot agree with this point more. The cash machines can have long lineups. Try and find one in the mall, at your hotel, etc.
One of the things you can do is check out the free movie screenings. Unfortunately, the bulbs on the projectors when my wife and I went weren't as bright as they should be, but we had fun watching The Lord of the Rings films with other fans.
Despite the craziness, there can be some real good things about going. I wish I was!
Oh...I think you should seek out Dr. Tran's Guide to San Diego Comic Con!