Not familiar with the Nikkor lens line up so I don't know the details on your lenses, but the 55-200mm is likely your best bet for most shots. Ideally I would want to shoot with something extending out to at least the 300mm range on a crop, as I found that even the 200 often fell very short last year.
Can't find the buffer size on that body, but apparently you have 3fps, so I'm guessing it isn't huge. Be prepared to be very careful with your shot timing, or you will quickly get frustrated when you run into a full buffer and it stops taking photos. (I kept trying to take photos while players were breaking out to dive into the snake, and usually would have the camera stall just as they were full into their dive. This year I have a 7D, so I no longer run into stall when shooting sports.)
If your lenses don't have some form of ultrasonic focus drive, then I strongly suggest making that feature a priority for the next lens you buy. Sadly, good glass is not cheap. (Even some of the 'cheap' glass is still annoyingly expensive.)
Keep your head up and watch what is going on. Don't get sucked into tunnel vision focusing on one player, as that is a great way to totally miss someone on the far side of the field shooting across in your general direction.
As for cards, as many higher speed cards as you can bring along. Keep spares in cases, and make it obvious which ones are 'used'. Better to switch out a half full card between games than find you get a 'card full' error in the last few seconds of a close game. (Plus, SD cards are cheap. Quality CF cards hurt the wallet.)
Originally Posted by Lrrpie-CT
I destroy drives for clients all the time. Sometimes, intentionally.