The 24-105 is NOT a typical focal length for stadium football so as Rick noted, it is very important to know where you are shooting from but also WHAT are you trying to cover?
I shoot football from the sidelines and the end zone and my typical lens setup is a 400 f2.8 on one body and a 70-200 f2.8 on the other and most of the shots with the 70-200 are closer to the "long" end of its range. At times I will use a 200-400 f4 with integrated 1.4X extender while some people prefer a 600 f4 over the 400 f2.8 for its greater reach but in general a 24-105 is a really short lens to use as a primary field sports lens even from the sidelines. So you will want to be as close to the action as possible.
If you have sidelines access, be very aware of the requirements of that facility, the officiating crew, and of course safety. And don't cut across the working space of others or you will make enemies in a hurry. Players and officials are the important folks, get in the way of them and you will at best be removed from the sidelines and at worst run over. Situational awareness at all times is key and the best way to get hurt on the sidelines is obliviously reviewing your last capture while another play is starting; field boundaries are only rules and NOT physical and players often end up well across the sidelines.
With decent lighting, you can go faster than the minimum action shutter freezing speed of 1/1000 and 1/1250 or 1/1600 will likely be good choices depending upon the lighting. If your 24-105mm is well behaved at f4, then shoot wide open even if you don't need to for the light because classic sports photography generally tries to isolate the player(s) of interest from the background. I always shoot sports in manual exposure mode with ISO set to auto. Capture your photos in RAW so that you can do the most with them in post, RAW saves all of the original capture data allowing a lot of adjustment when necessary in post.
As to focus, I use a pretty simple servo AF setup with the case set to optimization for random movement/speed change. The camera can do a great job of looking at a scene and focusing on player eyes (if visible which they often aren't during a football play) BUT you need to choose the subject that matters in a given play. So I use either single point or single point with 4 point expansion to have full control over what subject is covered by the AF point.
Placement is critical during daylight because you want to avoid having your players back illuminated by the sun and this can happen even on fairly overcast days. If at all possible keep the sun behind you and realize that you may end up with strong contrast between brightly illuminated and deep shadow areas which can somewhat be corrected in post IF you shoot in RAW, shooting in JPG imposes far more limitations because much of the original capture data is discarded during conversion reducing your ability to make radical corrections in post.
Rodger
EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video
