Once you've internalized the concepts necessary for team play, and can control your movement comfortably, the next step is to focus on accessing the current situation to better inform your decisions.
Try to pay attention to your position relative to the other players in the game.
If you're too far away from your partner, it makes it that much more difficult for both of you to help each other. Often times you may need to double back from a position favorable to you, in order to create a better overall situation.
One of the most common blunders for beginners is being unaware of your partner's whereabouts because you're moving the way you personally want to.
Be sure to also take into account your partner's current health. When a player gets taken down, the game temporarily becomes a 1v2. New players will instinctively try and be aggressive when their partner is low on HP in order to help more, but this often results in getting ganged up on after the partner has been shot down. When your partner is low on HP, consider leaving yourself in a position to disengage if they get shot down.
The lock on warnings are warning arrows that appear at the edge of your screen in yellow or red. Yellow arrows will appear when you're being targeted by an opponent, in their position relative to you. If they fire at you, the arrow will turn red. You can figure out when you're being double locked (locked on by both players) using these alerts, as well as use them to better avoid fire from outside your field of vision.
Located in the upper right corner, the radar is quite convenient for confirming the location of players outside your field of vision. For instance, if you landed a melee on your opponent A and you want to do a combo, but you're afraid of being cut. The radar is useful for such situations. When A's ally, B, is heading straight back to you and your alert turns red, before he cuts you, you can deal with him either by quickly doing some evasive maneuvers or moving to intercept him.
It may seem difficult at first, but building an awareness of the radar will pay off in the long run.