I have an Canon Powershot S2 IS and I have a two part question on settings.

Well, the first thing you can do is reset your camera to factory default settings. That'll at least get you out of the basketball settings. Then you simply do what you did before, only customized for football. As Aditya recommended, set it to program and then adjust the settings accordingly. You're going to want your ISO to be at least 400, otherwise you won't get a shutter speed slow enough and the aperture settings wide open enough to balance the lighting conditions while preventing camera shake. Also, you may want to use the exposure compensation. Luckily, night football games tend to be well lit, so you shouldn't have that much trouble there. But I'd also consider getting a monopod for additional support against camera shake.

Also, you can avoid alot of shutter lag by doing the following:

1. Prefocus. Hold down the shutter half way to get a prefocus of the image you're shooting. When it changes, prefocus again. This will speed up your camera's performance during picture taking since it won't have to autofocus before it shoots the shot.

2. Use faster SD cards. Yes, there are faster cards and it does make a difference in writing the image file to the card. This is especially key if you're taking multiple or burst images.

3. Fresher batteries. Use alkalines at least. But I recommend using high energy batteries designed for digital photography. Varta is a good brand. They are usually sold in camera shops, are long lasting (because they are sold in small quantities) put out alot of energy.

4. Pan with the action. You can create some pretty cool shots by panning with your shot, focusing on your subject. This will create the effect of your subject in sharp contrast to the blurry background.

6. Stick with 100-400 ISO. Going higher will cause more noise/grain in your shots, particularly in darker settings.

Doing these, particularly prefocusing and panning with the action will cut your shutter lag by as much as 80%.