Purchase better boots to gain extra power and effect stats.
Coins
Watch advertising videos to 20 coins for each of them.
Defending
When blocking shots, watch the trajectory of the incoming ball then drawing a line from your goalie to it. If timed correctly, he will block the ball. The speed of the line being drawn affects how fast the goalie moves.
Shooting
When taking goal shots, draw a line from the ball to the goal to aim. The speed of drawing the line is important, as it affects the ball speed. Draw a line from the ball to the circular target placed around the inside perimeter of the net to get maximum points. The target will be marked with a multiplier indicating the amount of bonus points for a successful goal. You can slowly draw your shot for increased precision but less power. However, a precise shot is sometimes better than a powerful one if it cannot be blocked.
Enter to the "Special" tab of a player's stats screen to access special shots. Use them to fool the goalie.
Shoot at the sides at medium or high height because those are the most difficult shots to block. Also try to make your shots curve.
Training
Due to the time required to train players, use all your energy and coins before starting a training session. Focus on training the following skills in order: Power, Effect and Stamina. You can train two players at the same time.
Spend coins on upgrading special skills. Recommended skills are the Panenka, which tricks players in online matches, as well as Foot Change. They are not effective in multiplayer mode against real players. Use them in single player modes.
Boots...