advice please on how to take foorball games

[roi]

i have 2 friends playing on a football team. i've been taking pictures for them from the stands since last season with my canon digital rebel xti. up to this point i have stuck with the automatic sports mode to take all my pictures. mostly this is due to my lack of experience and knowledge with photography. i think i'm ready to start playing around with the manual settings now...

i acquired photo credentials for this weekend's game (friday night) so will be on the sidelines taking pictures. as mentioned, i have a canon digital rebel xti and am using a sigma ex 70-200mm 1:2.8 lens. if i decide to venture over into the manual settings what recommendations do you have? what sort of range should i use for the shutter speed and iso? i'm thinking AI Servo auto focus mode with center focus only would be good, is this a good assumption?

i'd appreciate any advice! thanks.

[Wills]

Although I don't shoot much football, when I use the 70-200mm lens I always set the focus point to centre or left or right of centre - but only one point activated - more than one focus point active slows up the focusing speed tremendously and I find I start missing the shots. AI Servo is preferable, but sometimes I shoot without it, but I would set it on. Manual settings - hmm I don't think you have enough time to get fiddling with that if you are going to wait for a shot so I would decide what it is I wanted to achieve - IE DOF or stopping the action and set accordingly. If you want to stop action you need high shutter speeds - set the camera to Tv - set the speed you want and the camera will choose the aperture - dial in EC if you need.

If it is DOF you require whereby you want to isolate a subject from the background (by making it out of focus) use Av mode, set your aperture to 5.6 or whatever will give you what you want and then allow the camera to choose the shutter speed.

Don't shoot much sports, but these are the principles I apply when shooting unpredictable fast moving people/things