On this video tutorial by photographer Nathaniel Dodson (from the website tutvid) looks at how to add a J-cut transition in Premiere Pro in a few different ways that will give your video more production value and a more polished look and feel.
So what is a J-cut – well, it gets its name from its shape – basically we are talking about a cut (scene to scene transition) where the sound is cut before the image and so you have sound “entering” from the next scene before the image changes (the name J-cut comes from the J like shape that this transition creates in the timeline).
So how do you do this? the simplest way it to just unlink the video and audio (right click on the track in Premiere and choose unlink), but Dodson actually suggest a different method – using the rolling edit tool and alt you can choose only the video (not audio) part and move it forward creating a J cut where the sound enters before the video.
To improve the J-cut, even more, you can apply a wide constant power crossfade audio effect between the two audio tracks that are in the J-cut – this will give you a more smooth sounding transition.