I have been covering my local clubs for sometime now. I use a Nikon D3100, with a Sigma 70-300 lens. I always stay on the outside, so that I can wander around the ground at will. My favourite location is the halfway point, you then do not get linesmen running in front of you, or halfway to the corner flag.
I prefer to use the camera on its sports setting in auto. That way you need not worry about the focussing side of things. The action tends to come in bursts, so a knowledge of the game is a good start. Another thing I love to do at games is work the crowds, have a talk, laugh or take their photo. That way, they will go looking for themselves on your site, they in turn will let friends know and so it goes on. Or hand out cards with your details on. On matchdays, I start with the teams warming up, then coming onto the field and then the game itself. I also look for that amusing look, action etc.