Anyone on the field can end up tackling, the question is when should you tackle. First, you want to study your opponents' strengths and weaknesses. These are all clues to how your opponent will try to beat you. The tackle must follow a fail-safe philosophy. Your challenge should take place in an area and at a time when there is the least danger if your tackle fails.
Timing is the key.
You must be alert to the flow of the game and have the speed to be in the right position at the right time. Ideally, the right time is just when your opponent is playing or receiving the ball. You must be aggressive, don't let the attacker dictate the situation or area of the field. Guide your opponent away from the goal and towards the touchline if possible. But the ball carrier isn't your only concern.