Fast Bowling Tips

Efficiency
Your body is as efficient as you make it. If you are stressed out by work/school and sit on the sofa in the evenings eating crisps you end up tired, overweight and hunched over. If you train regularly, activate your cricket playing muscles and feel relaxed about things you become an efficient athlete. 
Time
 There is never enough time unless we make some. Practice and train more than you play because it has a direct pay off on the pitch. Even hopelessly busy lives can find time for a couple of bodyweight training sessions a week or turning up an hour earlier on match day to get warmed up.
Capacity
Cricket is not an endurance sport. It's a power based game that lasts a long time. The difference is between endurance and work capacity. With the latter you are able to recover between spells and overs more quickly rather than just being able to jog miles. You train cricket specific work capacity with interval running.
Balance 
Commentators often talk about bowlers having a balanced approach and action. Being able to balance in a dynamic situation (running, throwing, catching, batting) transfers directly to bowling performance. The better your dynamic balance the better your technique and that means faster and more accurate bowling. Bowling is the best way to gain balance, but you should also include plenty of single leg training, bodyweight training and balance drills in your workouts and training sessions.
Specificity
Everyone agrees that training for cricket means playing cricket. Where there is controversy is how specific the rest of your training should be. Running, for example, has more crossover to cricket than swimming. The rule of thumb is this: you are specific enough if your training is in 3D, standing up and based on speed, power and strength.
Planning
There are a lot of factors that go into improving your bowling: speed, strength, power, technique, experience and the rest. That's why it's important to have a plan that you stick to throughout the year so you are doing the right training at the right time. Know your season, know your own strengths and plan around them. You also need to have regular checks to ensure your plan is moving you towards your aims.
Progression
Whatever you are working on you need to progress. That may mean more weight, faster sprint times or longer interval workout but you should always look to improve your fitness until you are the best you can be. The result of your work will be less injuries and a better performance.