An easy way to improve your stamina is through interval training. A simple way to do interval training is to do multiple 100m sprints while resting for a couple of minutes in between each sprint. This way you will be building up your stamina to run long distances without getting tired quickly. Skipping rope is another excellent exercise which helps in building up stamina. Skip for a minute then jog slowly for another minute in order to recover, then skip again for another minute. Initially do this for at least 4 to 5 minutes. Each week try to increase the amount of time you skip so that you can easily skip for 10 minutes or more.
You can also try other exercises like running on the spot for 5 minutes daily. Run for a minute, then rest for 20-30 seconds. Keep repeating until you have run for at least 5 minutes duration. Swimming and cycling are other excellent exercises as they can help in massively building up your stamina levels.
Another excellent drill to increase your stamina and endurance is to dribble and run on the soccer pitch. Stand on the touchline with the ball at your feet. Dribble the ball as fast as you can while running towards the center spot. Now leave the ball there and run fast towards the opposite touchline. Come running back to the center spot and then dribble the ball as fast as you can back to the starting point.
Not just exercise, your other lifestyle habits can also have a tremendous effect on the overall stamina and fitness. You should try to eat healthy foods, avoid unhealthy foods and drink plenty of water throughout the day. Try to maintain regular sleep schedule where you are getting at least 6 hours of healthy, peaceful sleep.
Most people want to get 8 hours of sleep everyday but in my opinion the quality of sleep is more important than quantity. If you have a restful, undisturbed sleep for even 6 hours you might feel fresh and energetic when you get up in the morning. Studies seem to point out that retiring to bed early at night can improve the quality of sleep. So try to avoid staying up late if you want to enjoy higher levels of energy during the day.