There are several skills that can greatly improve your effectiveness in a real life defensive shooting situation. Not just the fundamentals that every noob gets in a basic class (grip, trigger control, sight picture- try this and this and this for more info). The video above does a good job detailing fire from cover techniques.
To add context to this : I am focused on building up the next level of skills- travel (move off the X!) and using cover/concealment (present the smallest possible target to the threat when you engage). If we truly fight like we train in high-stress situations there could be a lot of people standing their ground in the open – like they're standing at a range lane, right?
The ideal technique – realizing that training only takes you so far and every situation has unique challenges that must be solved on the fly- is to instinctively use travel skills to move towards cover (something solid that could protect you from incoming fire–ideal scenario) or concealment (something that hides you from the threat but probably wont stop incoming fire–second best but better than sticking out like a signpost on a desert highway). That moves the advantage needle back towards you – and I like having the odds stacked up that way.
To get back to the video piece of this – IDPA rules dictate that 50% of your body must remain behind cover when cover is available on a CoF. Keep that in mind watching the video. That means that you need to keep your feet behind the barrier and lean out to the left or right in the first part of the video.
The second part of the video is awesome- you can see how the trainee is firing from a concealed position and how it looks from the threat perspective. Ideally when he engaged and went low he should have been backing away while firing before dropping – but that's not the drill script here.
The Operator-level use of this skill is to randomly switch target engagements to avoid becoming predictable: ex. Lean out strong side for shot or string 1 and pull back behind concealment. For string 2 squat down and engage from left side of barrier, pull back behind concealment. String 3- return to standing and lean out from left side. The key here is to NEVER use a rhythm to prevent the threat from guessing your next appearance.