I was talking to a novice Pro Tools user recently who was using Quick Punch to punch-in to record because they thought it was necessary to punch-in. That isn't what it's for but it did make me think it was a subject worth covering in a quick Pro Tools Tips post.
What Is So Clever About Quick Punch Anyway?
Quick Punch allows the user to instantaneously punch in and out of record. This is a nice way to record if you have physical transport controls as you really get the old-school tape machine experience if you have a button to actually punch, but it's not necessary - though I feel slightly dissatisfied clicking on a graphic.
The really useful bit is that in order to enable seamless switching between playback and record Pro Tools is recording all the time it is in playback prior to the record button getting punched. Because of this it is possible to trim back to a point before the record button was hit allowing you to choose your punch in point after the fact.
A word of caution, this background recording does of course have an impact on system resources- You don't get anything for free.
Free Tutorial Video
Watch the short video demonstration to see this technique in action. I've added some telephone futz to the recording of my voice to differentiate it from my live voice-over.