Rule Number 1: Natives still call this stadium The 'Stick. They always will. Nobody calls it "3Com" or whatever this year's sponsor is.
The stadium was built in the late 50's/early 60's (I forget which) and instantly became a famously hideous baseball venue (from a player's perspective, not necessarily a fan's), thanks to the swirling winds. For football, I didn't notice this as an issue - possibly because of the way the seats were configured.
I attended a Carolina-49ers game in December 1996. This was the year that both teams were vying for the Western Division crown and a first-round bye. Going in, everyone knew that the winner of the game would take the title. It was a fantastic game with lots of offense on both sides, and an eventual Carolina win.
We bought tickets in front of the stadium. While I'd never recommend this as your primary strategy when attended a sporting event in a strange city, it was very, very easy to do at the Stick. The Niners were actually *good* in 1996, and it was a buyers market all the way. We paid $10 below face value and sat in the lower level at about the 40 yard line, about halfway up in those temporary bleachers that occupy the baseball outfield (these seats may now be more permanent, given that the Giants are over at Pac-Bell Park).
Niners fans are very wine-and-cheese. Not meant as a knock on them, but most of them are not terribly concerned about the game. We sat next to a very nice man and his wife, both in their mid-50's, both lawyers from the Sonoma area. They had season tickets, and brought their own grapes and cheese to eat during the game. The guy had been attending Niners games throughout the 90's (usually with clients), yet he was fascinated when I explained to him how you could sometimes predict the next play based on a shotgun formation with extra receivers on the field (he'd never correlated third-and-long with an extra WR in the game).
A thoroughly enjoyable day...good weather...good game...good stadium (for football, anyway). Traffic in and out is a major pain, so ride the bus if you can (buses get priority getting in/out, but it's still not easy).