Twenty20 bowling is about limiting scoring by stopping the batsman playing his best shots.

Unlike longer formats this is not done through bowling a predictable line and length. This approach simply gives the batsman the chance to play his premeditated shots or free her arms and hit you all over the park. The solution is to have a range of different lines, lengths and angles combined with changes of pace.

This is not easy. You know how hard it is to get one line and length right, let alone several, but with practice you can come up with some reliable variations that will allow your captain to set a field and be a success.

This is the traditional line and length that you see seam and swing bowlers aim for all over the world: On or just outside off stump, bouncing to about hip height. It works best early in the match. The ball is new and more likely to swing or move off the seam. Batsmen tend to play less risky shots so you can be a little more predictable with the ball and try to get wickets.

The exact length may be forward slightly for swing bowlers or back slightly for seam bowlers but the idea is to put the batsman in two minds: play forward or play back? Any indecision leads to false shots and edges behind.

On slower pitches the approach may be fuller and straighter to try and hit the stumps or bring in LBW, however bowling too straight normally leads to easy runs through the leg side. It's important not to bowl too wide outside off stump on any pace pitch as the batsman can throw his or her arms at the ball.

The yorker is a quicker ball aimed at the batsman's feet. It's hard to hit for runs and just as hard to bowl right so needs lots of practice.

In the picture there are two lines. The red line is the yorker aimed at the stumps, ideally with a bit of inswing. This is good for a variation early on or bowing at the death of the innings. The yellow line is a wide yorker which is more defensive but even harder to hit so is a good variation for bowling at the death.

This very defensive tactic is designed to cut off scoring on the leg side. The right arm bowler goes around the wicket, aiming full and as wide as possible without it being a wide on the off side. The deep fielders can then be set on the off side boundary as it is almost impossible to play the ball to leg.

If the bowling and pitch is quick enough you can follow the tactics that England and West Indies successfully tried against India in the World Twenty20: Bounce them out.

The trick is not to bowl balls that bounce over the head of the batsman as this is a wide. However, getting the ball in above the hip and below the head is ideal. Batsman can only attack by hooking and pulling, which is hard against genuine aggressive bowling at the body.

However, getting this wrong can be a disaster. Bowling short and slow gives the batsman enough time to hit the ball almost anywhere on the leg side they like. If the line strays to the off side the traditional cut or unorthodox slice over the slips can be played.

A good variation of this is the loopy bouncer, bowled at a slower pace. As the batsman is expecting something rising to his chest he can struggle to time the ball if it arrives much more slowly.

There are many variations of slower ball. Some come from changes in the grip, others are genuine different balls such as cutters or back-of-the-hand leg breaks. With all the types the key is line. At the start of a short game aim straight so if they miss you hit the stumps. However, you may want to adjust the line to outside off stump at the death, especially if the batsman is more leg side biased.

Again the key is to practice your variation in the nets before trying it in the middle. A slower long hop or half volley are easy to hit, a slow ball in the right place will be slogged up in the air.

Image credit: Durotriges

Line and length images supplied by PitchVision - Coach Edition. Available to purchase now for clubs, schools and cricket centres.

During his career, Shane Warne was one of the loudest opponents to coaches; famously saying the only use for a coach was to drive the team to the ground. Yet even he turned to a mentor in Terry Jenner when times were tough or he needed some external help.

Coaching is critical; as long as it comes from the best in a way you can understand. That's why we set up PitchVision Academy coaching courses; to present information used in the first class game in a way that is affordable whatever level you play or coach.

So how does it work, and how can you make the most from it?

What is an online cricket coaching course?

A course is a bit like a constantly updated, interactive coaching book.

I remember when I was younger being desperate for coaching advice (we had no formal coaching at our club). Every Saturday morning I would take the 10 minute walk into the local shopping centre and pour over the coaching books in the book shop. Occasionally I would be impressed (and flush) enough to buy one. I treasured every book (and I still have most of them) but I felt they still couldn't give me everything I wanted.

The focus was only on technical information and glossed over tactics, fitness and the mental side of the game. There was no explanation, little context and the pictures never quite illustrated what I wanted.

That's why, when I was setting up the course on PitchVision Academy I made sure the authors all the latest methods presented in several ways depending on your learning style: words, sounds, video or worksheets. I also made sure each course contains an exclusive forum for members of the course to discuss areas in further detail with the coach.

Because of my experiences as a boy, I'm aiming to provide coaching information so you don't feel the same frustration with trying to learn the skills of the game be they fitness, mental, technical or tactical.

How to use online cricket coaching

Each course is unique in its presentation but they all have common factors:

• Complete guides to the topic.
• Are authored by recognised experts in their subject.
• Is totally ad-free. You have paid for exactly what you get.
• Can be used by players or coaches.
• Presented in several different ways to match your needs (audio, visual, written)

Using a course is a step-by-step process. Once you have enrolled you have unlimited access to all the content, so let's look at an example of how simple it can be.

For example, you may be having trouble playing fast bowling off the back foot. It's a common fault to back away. Coaches see it all the time yet many don't know how to deal with it. It can ruin a player's confidence and stop them scoring runs against any kind of bowler.

You decide to prevent this and rebuild your confidence by improving your defence yourself and want some drills. A quick glance at the courses page gives you Gary Palmer's "Build confidence with solid defensive techniques and tactics". Perfect.

As you have a specific problem you make a mental note to go through the rest of the course later and head straight for the section to stop you backing away (In Chapter 2). Here is a small sample of that video:

The actual video is much longer and includes the progressions from the original drill. You also head back to chapter 1 just to get a feel for how the back foot defence should look when done correctly.

Other courses may contain worksheets or quizzes to help you learn the information, but in this case the technique is about getting the feel right rather than the concept, so it's time to practice.

Armed with your new drills you head to the nets with some mates. Instead of just bowling and batting mindlessly you now have a specific drill to work on and turn your weakness into strength.

After a few minutes of throwdowns you go back to regular practice. Now you have the right 'feel' for where your feet and head are you are more confident than before. You can, with a few more progressions, get your technique perfect, even against the really quick bowlers.

Sometimes it won't be that easy. Perhaps your problem is not directly answered in the course (although most are) or you feel something needs to be clearer.

That's why we have build forums into every course that can only be accessed by course members. It's a feature I am particularly proud of: The ability to interact with the author of the course and other players/coaches. It's one thing I wished I could do when I was learning the game and love doing to this day.

Some people are happy to learn by themselves, but for those who want the interaction, chance to learn through thinking 'out loud' and personalisation through questions the forums are perfect.

These courses come from our passion to pass on knowledge in a level of detail that has never been done before in cricket. If there is another version of me out there looking for the same things I was looking for, these courses provide the answers.

So I invite you to take a look at the course contents and see if there is anything you can use to make your game (or the games of those you coach) better.

If there is, then it's time to enrol; I'm confident you won't find anything better or more detailed online.