The wonderful Colin Mulvany explains how this works in a comment on a blog post by Angela Grant:

Avoid putting two mediums or two wide shots together [side-by-side]. Also, tight shots make great scene transitions between two similar shots. I’ve also found that by having a lot of tight shots available, my edits goes much quicker than if I had to cobble the edit together with two wide shots.

Even though the extreme close-ups are harder to get on the site, they will save you in the editing process!

The blog post links to a good example of a bad jump cut. Learn to recognize these so you can avoid making them.