The first thing you need to know is to play till the referee blows the whistle. The primary thing that you need to focus on is to get in the right mindset in order to beat your opponents. You need to be tough both mentally and physically and you never afford to lose your mindset even for a second or two.
You need to remember to get your hands on the defensive linesman and him as close to you as you can, just before you go ahead and push him back. This is going to allow the runner to find some space and then run through the hole into the gap on the pitch. Once he does that, you can go ahead and push the defensive linesman back on the floor or out of the way. Once that person is down and out, you need to move along and then look for someone else to take out and to create space on the pitch for him.
Watch video tapes of your moves and your opponents in advance so that you know what you have been doing wrong, and what moves your opponents make. This will help you mentally adjust for the upcoming game and your opponents. You can also try and help off your team mates by taking out the person you are marking, and then helping out to take out the person they have been marking. This in turn will see them do the same and make sure everyone plays to the best of their abilities.