Mentally and physically strong.....
Keep on marking player when defending all the time even if you are a striker...
If everyone of your team do exactly like this, now only see how efficient is your opponent's players techniques to get past you...
When attacking, always give your teammates options when he has the ball...Positioning is important...
Passing must be accurate all the times. There should be no mistakes at all since you're playing with 5 or 7 players in a small pitch....
The last part is you techniques....