Examples
If there is an enemy Xin Zhao, he will most probably jump on the ADC and will burst out the damage. If you are familiar with his jump range, you know it is very small and a ADC can easily out range him. At the same time, your tank should move in front of you tempting the jump on the tank. Now the ADC can re-engage with safe position.
You might think twice using your gap closers or escape techniques when there are enemies like Blitzcrank or Thresh. You have to predict when they going to use it. This will give you extra time to dodge those abilities.
Practice
From today onwards, before you start a fight you should go through the whole fight in your mind. Your story might be different from the actual one. Still you need to practice this. When you master this, you will see that you can predict much longer than your early days. Most of the pro players predict even the damage done by each player.
This is very easy when you play as a team, but when you play solo queue you have to predict moves by your team members too. Always think they will play optimally and plan for it. Always have a backup if they did not.
Start with planning 1 v 1 first and then try this on team fights. In team-fights try to predict the high damage dealers and players with stuns.